[PSUBS-MAILIST] Trailer Issue

[Jon Wallace via Personal_Submersibles]

Took the K-600 out on the road for the first time on the aluminum boat trailer I have been modifying.  Destination was a weigh station about 20 miles away and the empty submarine came in at 3065 pounds.  Towing was effortless EXCEPT:
Attached is a photo of the suspension equalizer.  The front axle is left, rear axle right.  The submarine placement needs to be almost directly over the front axle in order to get a decent tongue weight of about 10% to prevent sway while towing.  However, you can see that the front side of the suspension equalizer is quite a bit higher than the rear, and after dynamic loading on the road (going over a pothole or two) that spring eye and shackle actually "tops out" or sits against the trailer frame making for a very rough trailer ride.
If I placed the bulk of the submarine over the mid-point between the two axles, theoretically to spread the load equally between them, I would essentially have no tongue weight so I don't see that as an option.  I could always add some extra weight at the front to get some tongue weight but dive ready I will be close to the weight limit of the sub and trailer so may not have much wiggle room for extra additional weight.
Other options?  The shackles are 3.5 inch long, which is longer than a typical shackle, but I think designed that way to get the trailer frame as low to the ground as possible.  I could shorten the shackles to provide more head room between the spring eye and the trailer frame but I hate to do that work only to find out that it isn't enough and the equalizer just cocks more to the front and allows the spring eye to reach the frame again.  It would also end up raising the trailer higher overall which I want to avoid if I can, for purposes of launch and recovery.
I thought about stronger leaf springs but I don't think the springs are the problem.  The problem is that the load is primarily concentrated on the front axle and the equalizer allows the spring to pivot, to compensate.  So I don't see stronger springs preventing this.
I have also thought about "locking" the equalizer in place which would subvert the purpose of the equalizer.
Suggestions welcome
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