I'm putting a pulley reduction on my lift fan to actually get the thing to hover; what's peoples ways of doing the fan shaft?

It's got to be as short as possible as the Robin is pretty long and the fan's getting way too low in the duct or the engine's going to be sticking out a long way, or will remake the duct flatter on the hull.

I was thinking bolt pulley to fan hub, then 2 opposed taper bearings. Shoulder on the shaft pushes on the lower bearing and bolt tapped into the shaft clamps the top bearing against the lift frame.

Main problem at the moment is the fan's limited to 4500rpm so the engine is at 4500rpm also.

What are people's opinions on this? (without buying a new engine!)