Way to go GY!
Yeah, it’s currently too large for your tractor, but I got to say it’s easier sectioning and cutting something oversized to custom fit than starting from scratch…or worse taking one too small and enlarging it to accommodate a bigger tractor.
Speaking from experience (and IMHO) the most critical starting point is the base platform geometry and how it’s mounted under the tractor’s transmission and stub frame. Positioning and mounting the vertical towers is important but ultimately the base platform has to be affixed to the transmission and frame to spread the load, endure front flex and impacts and also act as the sacrificial component to bend or break (rather than any part of your tractor).
You will find four threaded bosses under the tractors transmission bell housing (9 mm ?). The mount (base platform) should be centered and drilled to a template that you can make yourself. I’ve used 2” masking tape, trimmed to fit the flat area of the transmission, razor cut the four holes, carefully remove the tape template and transferred it to 5/16” flat steel that’s long and wide enough to mount the vertical towers. The most common mistake people make is to assume those four bolts will be strong enough to hold the completed FEL assembly plus the weight in the bucket and it will NOT (I'm sure you've heard of tractors breaking in half). Spreading the load will mean designing diagonal gussets welded to the base, drilled and bolted to the engine block to adequately extend the strength of the base platform.
I’m struggling to make this sound less complicated but once the base platform is done correctly, the rest of the loader components will fall into place rather quickly.
Mark