I don't necessarily agree with forgetting the four stroke, especially if you're willing to take plenty of time with an instructor. He should be able to get you to the point of flying, and landing, well enough that you won't crash for at least that first few months.

The 70 four stroke WILL fit (a club member flys an LT 40 with one), and the plane will fly at about 1/4 throttle. The big thing is, that the 70 will work with MANY planes once you advance beyond the LT. A 52 four stroke is marginal for other 40 size sport planes, but would be sufficient for say a Tiger 2, or 4*.
Dennis-