I can see the benefit of a YOT build .being able to sling the seat under to lower the c of g. But what benefit from a standard Y against T frame,I can see that you can get the seat marginally lower but not by much before hitting obstructions, with T frame You can still get the seat and you,in line with the rear wheel centers . So any other advantage,that makes it worth the slightly more complicated construction to form Y and line wheels up.

Classes that do not allow any suspension maybe benefit from the longer legs on the Y frame to give some spring effect? Class 5 has rules like that. The T frame blokart has flexible plug in axles to give some suspension but it is a one design class that allows that.

so for me not worth the extra alignment issues ,I'll stick to a T frame for my intended next build.

Don't underestimate the benefits of getting the C of G lower and the weight further back

This is low as I go with my Y frame mini.

Yes I see the benefit,depends on how much clearance you have ,will have to have a look . A friend of mine has a potty and is always clattering the bottom on the sand,has damaged the seat and the frame, We often get large wedges of sea weed and I can bounce over it. He can't,has to go round it, or get stuck in it. Might do some calculations as to how low to go. But yes can see how it works.

Then make a timber axle mini.

the longer axles/better suspension is spot on, but be careful that you don't go too long with your axles as you can create a frame that loads up heaps of energy then lets it go creating a jumping frog effect where you go boing in the middle of the race. that wooden axle mini is the nicest i ever built, rather simple too ,built the frame in a day