Hi there Tom, let’s start with the differences.
The SG’s being the older design didn’t have a center ski, as well the tub tended to be deeper.
As things progressed the tubs became shallower and most often had the center ski.
All of that said Andy was always tweaking the design and the SGX may or may not have had a center ski and the final shape of the hull bow changed progressively. I’ve attached a couple pictures of my SG and 2014 SGX. These are 67 hulls but the changes to the 90 were the same.
I have also attached a reference sheet that used to be on Andy’s website that gives you the hull length details you are seeking.
As to prop types and sizes for a 90, that’s more difficult. Old school ABC props I have run everything from H32 and 38’s and up to 1667’s. Which one works is highly dependent upon your set up and pipe length. If I were you I would start with 32 or 38 and pipe length of 11.5. Then start experimenting from there. What you’re looking for is max RPM, final speed and turning performance. Then venture into the new ABC props, then more testing and strut angle is usually needed.
My perfect 90 set up is 11.25 and a pitched up H38 that absolutely tears the lake up. I haven’t needed to move beyond this position because of its overall performance.
Hope this helps.
