RF CLIMBING:

Wallclimb version of RF(Doesn't work, some have tried, even me):

Go into a wall(jump+buttstomp+jump with Spaz) and select RF. Hold up and shoot. You'll go up. The reason why this does NOT work is that when you are on the top tile, you shoot through the ground into the air.

Air version of RF(If you are a newbie of JJ2, you may not understand):

Go into a small gap(width 1 tile). Jump into it and SHOOT SHOOT SHOOT.... Sometimes you fall for no reason but if there's ammo on ground, you will eventually go up. !