RE: CG Ultimate or GP Super Skybolt?
Ultimate needs a few changes. Stock undercarriage wire is too soft. I made up a carbon fibre undercarriage. Reinforce the light ply on fuse top where cabane mounts (1/16" ply doubler worked well.. Invest in after market cowl. Spend some time making a good elevator split drive system, mine tended to screw out of loops a little.
I had an OS .90Fx in mine, thoroughly delightful plane. Don't still a heavy engine in it, it will ruin the glide qualitities.
Steve