well basically you just have to do as big guys. squirm in the bed lol. I use my mp3 player as a base to tell me when to switch positions hehe. 1 song in this position, then twist and turn and 1 song in that position etc.
and dont tell me its hard to spread your legs in there. its not like you arent used to it my problem areas are outside of my thighs (cuz the yare huge) and inside of my arms (cuz they are badass). So i have to twish my legs and arms over my head and crap.
basically what it looks like is that you will have to actually be on your stomach in the bed to get tanned allround.
Go do the stand-up booth(at the tanning place) or try to move more when u are tanning. Start off flat, after a couple of minutes- bend your knees....ect.