Pinion is a 0.5 mod. Motor shaft is 2.0mm. Robinson Racing makes 0.5 mod 2mm bore pinions http://www.robinsonracing.com/catalog/2mm_pinion.html#.5-mod
Hot Racing makes a 48p spur gear that fits so you could always change over to 48p gears.
I've done a few mods to mine.
The D115F servo...