This plane is superb, my last one had a ST90 in her and it was a great flying plane. I did not use the retracts and just jammed it by tying the push rods together then using CA to hold it. I just took delivery of No. 2 day before yesterday, last night I got the wings attached and the horizontal stab fixed. Hope to finish more this week. This one will have a YS110 in her as the weight of the YS110 is not far off other 90 sized engines. I think I will be going for a 16x6 or 15x8 prop. I wonder is she can prop hang?
As far as fixing her up there are not many tips, this plane is really easy to build. Just one thing, please secure the tail wheel properly, if you look at how it is attached, the whole thing can come loose with mere epoxy holding it. When it does you will have no way to work on it again as its really a tight area. I may leave mine to swing loose this time and not attach it to the rudder.
I think I will get a set of Robart UC, I will keep mine fixed like the real thing.
Your SA100 should give you about 8-10 mins flight time with the supplied tank. I used and will use the stock hardware, it works very well. My engine will be set up inverted as side mounting will spoil the looks of the cowling.