RE: Magnum w/ landing gear?
I don't think I would bother with the Thunder Tiger. I say buy once and buy right the first time.
My Magnum has a West .50 and runs in the mid- 140's in level flight. It starts right up like my MVVS .40 (which is probably the most reliable engine I have ever owned).
The low level high speed passes are so much fun with this engine and plane!!! A normal sport .46 (like the Thunder Tiger) simply won't do it for you, you will probably regret it as you seem to have a "need for speed".
I can barely reach 150 MPH with the West .50/tuned pipe combo, so I can guarantee that it is not going to happen with a Thunder Tiger!!! As erikpmort said above 110 MPH is a more realistic speed to be expected in level flight with the Thunder Tiger.