Yep! My UCD has a pre-Chinese ST 90 with a MCP spinning an APC 15x4w at 11,400 peak RPM. (The MCP cured the ragged mid range, and boosted the power by over 1100 RPM.) Plug is a Hangar 9 for ducted fans, but the OS #8 works good too. Fuel is 15% Mach 7 castor/synthetic blend.

m.gramling also tried a ST 90 in his UCD, but later gave up on getting his ST 90 to run reliably enough for a UCD. (I think he switched to an OS 91FX?)

Here's a link to a short movie of my UCD doing some hovering, an outside waterfall, and a low level wall into a hover. It's not much, but it shows that the ST 90 has adequate power for the UCD.
(note: for some reason the engine sound in this movie is very unrealistic. It does not sound nearly that loud in real life.)

http://www.eldonmo.com/video/ucando.wmv
(it's a 10 meg file so allow time to download)

And here's a photo of the UCD hovering.