Try an APC 12-4, or 12.25-3.75 on the TT 46 Pro, along with a Tower/GMS/Hobbico tuned muffler. That should help the vertical considerably & not cost a lot of level speed (you should still get 60+ mph). The 46 prop change & mild hop-up is quick & cheap & it will tell you whether or not you actually do need more punch.

If you really do need more power, go for the OS 50 SX, rather than a .61 engine. The 60's are only moderately more powerfull than your TT 46 Pro & are a lot heavier -- and as already noted, you will need to add even more weight in the form of ballast --- maybe for no net gain.