Also, the reason you got 4 pops of OD in such a short time is because of the elastic effect. His OD was so low (atrocious) that it trained quickly to narrow the gap between his other higher skills (maybe ID). I wouldn't count on his OD training anywhere close to as fast in the future, especially since his age and height will be working against him, and the elastic effect is decreasing.
You might be able to get by with him as an inside oriented SF in DIV, but in DIII and above he'd be better suited to being a PF. Plus he'd be a much better PF than either of your other starting big men once he's trained up.
Another option could be to train him to be a PF. Sell your current PF and acquire a better SF trainee candidate, especially a SF trainee with better guard skills. Then, as you're training your HoF guy in big man skills, your newly acquired SF trainee can also train up his big man skills.