U Can Do 3D
I'm running an APC 15x4w on my ST 90 w/MCP.
My nephew is runnng a TT Pro 61 w/MCP on his UCD spinning an APC 13x4w. It hovers and pulls out vertically at full throttle.....but nothing like the ST 90.
So with a ST 75 powered UCD, I'd suggest starting with an APC 14x4w.