I have been driving a pair for a number of years, albeit not 'all the time'. I began w/o lessons, though I've since taken a clinic with Hardy Zantke, along with other very knowledgeable ADS whips/judges! What I had going for me was a LOT of prior years of horse training/using experience.
I first joined ADS a number of years ago; was lucky to make some good choices in books from their list of titles-got a good deal of practical help from those books, which include "Make the Most of Carriage Driving", by V. and R. Ellis and J. Claxton-this especially helpful on basics; though the emphasis is on driving in the UK, it is a very useful tome--along w/ "Drive On", Doris Ganton's more 'advanced' book, and the phamplet on Turnout and Appointments from the CAA.
I own three pair vehicles...a back to back custom built English trap, a Glinkowski 'mini-mix' marathon vehicle(not the wagonette style), and an all-wooden buckboard. The trap is cut-under, but does have a 'reach'; the Glink is cut-under, w/ NO reach, and the buckboard has smaller front wheels(that will actually 'pass under' the wagon box), and a reach. Most maneuverable is the Glink. 4 wheeled vehicles will 'generally' have a higher center of gravity, so should have a reasonably 'wide' wheel base,AND, be cut-under w/ NO reach(the reach will still be a 'limiter'), for better stability, other things being equal.
Several years back, a couple began building the CUTEST little 'covered wagons' for minis! When I first saw the ads, I coveted one! BUT, in the course of my ongoing driving education, I realized the vehicles were actually pretty dangerous to drive, because they had a VERY limited ability to turn, due to no cut under, front wheels too large to 'pass under' the box, a high center of gravity and relatively narrow wheel base. When shopping for a vehicle, this is good knowledge to have!!
I'd recommend brakes on any 4 wheel vehicle you may use 'off pavement' or over uneven or hilly terrain. They don't need to be on all four wheels, however. In ADS, it is required to have either breeching or brakes on any 4 wheeled vehicle; sometimes you will see a more elegant turnout w/o breeching, but for practical everyday use, having BOTH is actually a very good idea, especially if the vehicle and its 'load' are possibly relatively heavy, and/or there will be any use over uneven terrain, or at speed.
To keep from writing a book, I recommend you research what a 'reach' is, and why it is pertinent;a 'fifth wheel' and its application; also, a suspended vs a drop pole, a 'crab' vs a pole w/ a yoke, types of brakes, etc.--whether or not you want/need an 'evener', and the like---as these may pertain to the kind of driving and vehicle abilities/limitations YOU would want. Also good to know...at least in the US, wooden wheel diameters are expressed WITHOUT the rubber tire 'inserts'--meaning that if you want wheels that have an 'actual' diameter of 26", you would ask for 24" wooden wheels, as the inserts are 1" 'deep', adding 2" to the 'actual' rolling diameter of the wooden wheels. I *think* it is the same for steel/aluminum wheels in North American-built vehicles, but be sure to ASK!
British/European-made vehicles differ; for instance, my UK-built Bennington cart has wheels that are @ 24" TOTAL diameter(they are expressed in cm), and the stated diameter INCLUDES the rubber inserts...on the Benny, the rubber is rounded, and nearly 2" in width. The Glinkowski is similarly expressed, and similar in width of the wheel/rubber inserts, though it is a 'flat' insert.
A crucial part of pair equipment is the pair reins, and the proper adjustment thereof; the Ellis-Claxon book refers to 'draught'(draft) and 'coupling' reins, and their proper adjustment is especially crucial, for it can affect how the pair works/pulls. This is an area where an experienced pair instructor would be MOST helpful, IMO.
Know that the most important 'match' between pair horses is probably how they 'stride' together--not their color, not even their height/build, but whether they move similarly at the various gaits--AND whether they 'get along' w/ each other, and are equally willing workers.
As for using a pole for a cart...I actually bought one for my Frontier for the first 'drives' of my pair(both of whom have always been trained as singles first; I have had several different 'pairings'; the only one I ever had a issue with was the least-experienced as a single; he 'leaned' to the outside in a pair hookup. I sold him for a single, so didn't really have to try to 'work him out' of that behavior!) I believe it was 'OK' for the initial and very basic pair hookups, but would not recommend it for 'regular' use.There is actually a
There actually is a pair cart that has been, perhaps still is, used for Freisians in their homeland...have seen video of it, but don't know how well it actually 'works'. The few configurations I know of--the curricle, and the Cape Cart, which is said to have actually worked fairly well?-were 'special' set-ups--one CD-Ler spent a great deal of time, research, and I believe, money, having a Cape cart 'replicated' for her mammoth mule pair...so it's not really what the 'average' driver would probably want to try....
As for pair harness...I got the one I use 'everyday' from The Carriage House, in FL. It is a beta biothane, utilitarian, ordered it with the 'parts' to be able to switch it to two 'singles. It is made by the same fellow who makes Country Carriages' similar beta harnesses..Yoni.
There are several good sources for mini pair harness nowadays. You do need to know what kind of ends are on the swingletrees to 'match' up w/ the traces. I'd also recommend buckle-in traces, AND the use of quick release snap shackles, at least for everyday usage.
This is far from a 'complete' listing, but is part of what it can help to know about vehicles for pairs and other side-by-side multiple hitches(and 'abbreviated', it's still nearly a book!!
Margo