BSharp - It looks like the cart your hubby made for you is similar to the forecart. The difference between both yours, mine and the OP's (IMO??) is that ours both have the tongue situated much closer to the axle - balancing the weight of the cart much easier than where the tongue is "attached" on the OP's cart.
Am I correct?
StardustandBreezey's mom- As I mentioned in my 1st post, the Fore Cart was made to have equipment towed behind it (for farming). That "balances" them and pulls them up/back more and also stabilizes the tongue (won't flip up if more weight added to the cart since it's either adding solid weight drug on the ground or an extra set of wheels). What I have seen done to balance a forecart for training is a couple of things - 1 - the forecart has a hitch attachment that a basket can be attached to and weight added. This can balance the tongue more upwards and "pull" some of the weight off of the necks. 2 - Tie weights to the back of the cart - but put the tie over the top of the seat rest so that the cart is pulled up/back. Neither of these options will stabilize the tongue though - it can become "too light" and flip up.
Having the tongue "flip up" can be bad - 1 - w/ your lighter weight harness, it could snap pieces (not saying it will) and 2 - it's quite annoying and also really interrupts communication/concentration between you and your team. If it also "scares you" (and it scared the "bejeebers" out of me to have that happen - I have a tendency to "freak out"), it will upset your communication/nerves w/ your team. That will transmit thru the lines to them. Of course, for training purposes, it's not bad to have your team (and you) learn to work thru such a situation. Preparation for the worst, so to speak
So, between now and when you are able to get different arrangements, you could try a couple of things.
You could go ahead and try tying some weight on to the back of your cart so that you can work with your team. Learn where to position your own body (while driving) to keep the cart properly balanced (usually a good cart will be balanced for "float" in the shafts when it's built). That makes you an active driver and a better partner overall.
You could see if you could add a wheeled wagon of some sort (you want pretty heavy duty) to pull that will help to balance your cart - again - up and back. On the forecart, the hitch pin area is level with the rear end of the tongue and the hitch attachment (receiver type - like on a truck) is lower - under the bed/floor of the cart. I'm not really the mechanical type - I'm not sure how to attach something like this to help you (where it should be attached. The strongest point is going to be the axle/frame of the cart but not sure that would help your situation.
? for you - If your cart is sitting where the tongue is actually level - where is it in relation to your horses? Is it above the breast collars? Below the breast collars or level w/ them and the traces?
Here are some pics of my girlfriend using her Fore Cart w/ "farm equipment" (sized for ATVs or lawn mowers). Her's is pony sized, so a bit smaller/lighter than mine.
I don't have a close up of her attachment. It does help to stabilize the cart - though with the lighter weight towbar on the "wagon" the cart could tip back and bend it... It hasn't thus far.
The disk is actually two garden disks attached to each other. This can be pulled on one side with the 2 horse evener attached directly to the tow bar (driver walks on the ground) OR attachd to the Fore Cart from the other side with the ball hitch they have attached.
This is a homemade drag made from a 2x4 frame and chain link fencing. It breaks up manure in her pastures.