I mean, that'd still make it somewhat OP, I think.
Though to be honest, your approach is similar to what I actually came up with as a consequence for a different superpower (time-space manipulation--which I think is a lot more energy-intensive), in the sense that it'd take energy from the least important part of the body to the most important.
However, I suppose just having the energy requirements already limits a lot of the OP potential of the superpower (can't just summon a black hole, lol!), so I think your changes are quite reasonable.