Follow standard procedure for assembling a trailer wheel hub for installing the swing arm onto the idler hub. The idler hub is a 3000lb wheel hub mounted in reverse.
The difference when assembling the idler hub is you do not want any play in the idler hub bearing, you can do the castle nut up tight and not back it off before installing the split pin.
The idler hub only needs to be free enough to rotate, there is no concern of it overheating with an over-tight bearing. In fact the tighter the bearing the better.
Do not tighten so tight that the swing arm cannot rotate, but enough to take all play out of the bearing.
Use good quality trailer hub grease on both the wheel hub and the idler hub.
The grease can be added after the hubs are assembled with a grease gun.
Fill with grease until it protrudes through the outer bearing. Take care to keep the bearings clean and free of debris.
If you require additional support, please get in touch with the Futura team directly, and we will gladly assist you in resolving the matter.