Great idea, but I am thinking NO !
1st you have to remember that those are grease gun magazines, thus the lower is different and so was the modification to the USC magwell ( if any )
2nd, if there was no modification to the USC magwell for the TN lower, then you would have to modify it for the UMP lower regardless because of the double stacked magazines...
3rd, UMP lower = foreign part. I don't know how many US parts were used in the TN conversion, but if they used the exact amount, then you would have to trade out another stock USC part to compensate for the UMP lower ( all that '89 EO bullshit again)
I'd say it would be possible, but it wouldn't be as easy as you are thinking.
I can tell you one thing though.... TE is charging too much for their conversion.
I mean they are basically charging 600+ bucks to put on a 5 dollar aluminum block !!!!
That is highway robbery !
Of course they fix the magwell issue and exchange the fire control parts, but that is still way over priced for what it is.
For 625 dollars I would expect a Pro dye job, UMP slot cuts, the UMP conversion, and a TE supplied UMP lower....
Now that would add up to a decent 625, but all they do is dremel, exchange control parts and add an aluminum block.
They don't even have mags, lowers, or stocks on hand for customers.
So far this is custom work so the price should be higher ( not in the 600 dollar range though ), if they start doing non-NFA conversions, then that price had better drop else it would be pointless to use them.
With that said... I think TE does an amazing job of putting the parts together and I have supported them in the past.... I love it when a US company finds a way around retarted US and foreign guidlines. I just think that TE is robbing people on this conversion.
I mean how much could a block of AL & "gunsmith" work really cost ???
I love you TE..... but 625 dollars, give me a break !
Highjack over
ETA : KogaShuko, if you figure it out let us know.... It would have to be way cheaper than a TN or TE UMP conversion... so I say good luck if you try it