About axle slippage (apologies if this is patronizingly obvious): When I got back into cycling a few years back Datako on the Dahon forums explained to me that I ought to tighten both bolts simultaneously to, I guess, distribute pressure evenly. . . I can't remember if it was his advice or me just figuring out the obvious, that the hub needs to be secured whilst the bike is on the ground, not suspended from a stand, i.e. the frame has to bear weight down on the axle as it would whilst riding, otherwise a jolt whilst riding will likely move the axle slightly and tension will be lost. I find it a PITA trying to secure hub gear wheels with the bike standing up, making sure alignment and chain tension is correct. . . it's fiddly.