Yes, the .40 LA will fly it, but it could be marginal. The NextStar is a 6.5 lb plane. Also you'll have to modify the nose to get the engine to fit. I was going to mount a .40 FP on my son's NextStar but found it would require surgery on the nose to fit. I'd recommend going with the .46 AX. The plane was designed for it and it's a bolt-in. Attached is a picture of a .40 LA that I placed next to he .46 on the NextStar. You can see the definite difference in length.

Hogflyer