The P38 can actually climb vertical very well, especially right after take off. If you climb manually going a bit slower than the climb charts you can actually climb much more steeply compared to if you hit altX, however you will be going a bit slower once you level out. I like to take off, circle the base 2 or 3 times using a spiral climb, and be about 10K in under 5 minutes. So I'd recommend manually climbing almost to stall limits to gain alt, then level out after you climb to gain speed the rest of the way.