In his last Contri about mounting tubs on to rims, Ted Ernst touched upon the problem of making sure that the valve does not move, or lean etc.
This has always been a problem, but the associated problem arises from the difficilty, often of ensuring that the base of the tub, in those points immediately adjacent to the valve, sticks down to the rim...otherwise you end up with a little hump in the tub, which doesn't lead to very smooth riding.
This was a real problem in the 50/60s when valve seatings within the tubular were not as compact as in recent years. The way I learned to overcome this problem was simplicity itself.
As soon as you place the valve through the hole in the rim, you strap the tub down to the rim with a couple of old two straps..or four - two each side if you have them. Alternatively you can use a strong shsoe lace such as that from a soccer boot that is both long and quite broad. With this you simply wrap the lace/cord around the tub and rim for a few inches each side of the hole.
If you do this you will never have the tub "creeping" or the valve twisting or tilting as youn strain in other parts of the wheel to get the tub on.
Finally when you remove the straps/ laces, when the adhesive has set, the tub will be well and accurately bonded to the rim..and the valve perfectly upright.
Norris Lockley...Settle UK