Appreciate the advice, actually, %98 of this year i've trained centers and for a couple of weeks (Big mistake two position training) c/pf in inside scoring. I'm going to take your advice and down grade to lev 4, get one between 11,000 and 17,000. But i've taking people's advice before, especially with my arena and it paid off big time, and i thank all of you who haven give me the advice especially about my arena, about raising ticked prices.
Two position training isn' bad. I don't have experience with the bigs, but I'm training guards and every week I've been in the game until this week I've two-position trained guards in something (pressure, 1 on 1, passing or outside/jump shooting). Since I joined just after the allstar break last season and took the finals to three games, this was my first week with only two games and it was pretty painful!
The thing with two position training is that it allows you to improve more players nearly as fast as the single position does. So you could likely fully train 5 C/PF types and get at least partial training on a sixth, rather than just 3 C's. Of course, single position improves them faster, so there's nothing wrong with that either. But the important thing that you seem to be getting now is to keep working on your big men, and get older players for your guard and SF positions.