I believe that you can also use bootstrap recovery. It's not as good as safestrap because it doesn't use slots but I am pretty sure you can accomplish what I think you are asking. That is, you can erase the stock rom and install a custom rom that has all the space that stock has. The only drawback is that it's not as 'safe' as safestrap. If your custom rom is hosed then you have to reset your phone with fxz.