RE: engine hydrolic locking
Some info first. Is the engine fully broken in, or is it still new? And is it an ABC engine or ringed? I'm guessing that it's different now than it was before you taxied the plane around.
Engines don't hydro lock while they're running. That happens while you're trying to prime them. And unless you put the starter to your engine while it's hydro locked you won't hurt anything. Once you clear it up, there are no lasting effects (unless you did damage with the starter)
If I had to just guess, and I do, I would say you ran it lean. You should ahve seen some indications of it, though, when you dissassembled your engine. It might just be a combo of a new engine, good compression, and if the LHS assembled it with oil, that will have the affect of boosting yoru compression and make the engine very hard to turn over.
Does it turn with the glow plug out at all? If it gets tough with the plug in, chances are there's just excess oil on the top end, turn it over a bunch of times with teh plug out and see if that makes it better.
Let us know!
Andy