Reverse Spreaders

In terms of technical assists; you might consider reducing your shroudbase, if you are allowed to, either by moving the shroud attachments forward, having 2:1 blocks on the lower shrouds, or by having adjustable fore and aft tracks, these would get the boom further forward.

It is possible to make the spreaders "limited swing" usually this can be achieved with a clevis pin behind the spreader, or wiring, to stop a major mast inversion (which is not just a metal mast problem).

However I think that the classes that have swing or limited swing spreaders at least let off their leeward shoud tension, with levers or multipurchase blocks.

One interesting device produced by Selden's (for 470s I think) is an extended gooseneck, where the pivot is some 2" aft of the mast, the effect is for the boom to square off far more when it is against the leeward shroud, the main downside as I can see, is that it you tension the foot while the boom is squared of, and forget to let it off when sheeting in, you will do considerable damage, but this might be prevented with a screw to limit the clew to the black band.

Having had a quick peruse of the Solution rules, all of this might be illegal (together with your spreader proposal) because you appear to be extremely limited to what you can do to alter the boat from the "as supplied" configuration.

Probably the best way of learning to sail deeper will be experimentation, practice and time on the water.  When I look at the back end of the fleet, these boats tend to be sailing with too much kicker, are sailing too square, and are not particularly dynamic ... I am not suggesting cheating, but you do need to search for wind and adjust to changes in direction and velocity.