For what it's worth, a LA46 with venturi only weighs 0.8 oz more than a stock Thundertiger 36 without venturi. I just weighed both without mufflers. If I was going to use either with the Gieske Nobler, I would want to use a Tongue muffler to hold the weight down.
Of course you probably want a bigger prop for the LA46 than with the TT36, so that might add a bit more weight depending on how you choose.
I am a little surprised about the negativity on the LA46. It isn't any heavier than the LA40, a common engine these days for Nobler-like planes.
If you have an LA46 already, I'd say use it. You just have to prop it to use the power correctly. I would think one of the Master Airscrew 3 blade props might work really well. But you might have to play with it to get things right.