In addition to Quicksilver, I'd like to say the propshaft (stuffing tube actually) could use some support in the form of a triangle glued between the stuffing tube and the bottom of the hull, as the propshaft is unsupported for an unhealthy long stretch.

If the propshaft is the same as in the Kyosho 'Windhopper' (I'll explain) it's wise to change it for one with M4 thread; as replacements for the odd Kyosho size is very hard to find. With M4 threaded shafts the choice is considerably wider.

If it's indeed a Kyosho copy, don't get your hopes up too much on making it go faster; the rocker in the hull makes it porpoise (badly) beyond a certain speed, using a 600BB on 6 cells will be driveable, add one cell and you'll spend more time in the air than in the water...

I've tried to modify one for a friend and have gone back to a Graupner 34,5K prop and six cells.

Regards, Jan.