"Any" is a relative term... eventually you'll run into spatial difficulties (ie run out of room).
Errr... why are you using the 61t spur, btw??
Shouldn't you be using the *smallest* 55t spur instead?
61/25 gives 6.34:1... this is by nowhere "high".
With 55/25 you'll get 5.72:1.
If you can stuff a 55/27 in, you'll get 5.3!!
Don't know too much about the P2K2; I run my torquier P2K
at 5.46:1 on a very large track. I just unwrapped a Monster
(higher RPM design?) last weekend too, on the same track
it wants 5.77:1 to keep up with the P2K. Might have to try
1t less to see if I can get more infield speed, but the Monster
isn't getting overly hot @ 5.77 - definitely cooler than the batts.
Anything higher and the Monster bogs down even more.
Square or some other Jap optionpart maker made a spurgear
holder for EvoI/II/TB01 that takes standard spur gears.
If you want to experiment with gearing, this part is very handy.
I prefer to use 48dp gears rather than Tamiya's metric AVs.