Yeah, I have played with different ways of balancing the unit and seperatly using the hand balencer compared to items from RTI and even though there is no difference is vibes from the engine onto a test stand, wood, etc there is absolutly no difference between the two. Now looking at it upon a digital balencer their has got to be some differences, no matter how good you hand balence it. Im just referring to the outer differences and bearing wear at say 45 / 50 cycles, now in the longer run the may be some horizontal wear in the bearings, etc but in the short term I can not see a difference with one that has been hand balanced correctly.

I also took a hand balanced unit (wheel, compressor, shaft) and broke then down and rotated each one to a different position to check results from that and I still could see/hear/feel any differences. So with all this being said, I too think you will be fine to run it without balencing it first, if there are any balencing marks on the back of the compressor then its more than likly balanced, put it together and spin it up to say around 20K if everything feels okay, then make sure everything is tight and fire it up, you can always shut it down with the FADEC anytime something does not seem right, if its close then its not going to "grenade" like many people fear.