Any reason to use more than one layer of duct tape? Can’t think of one if it’s well applied…

Can be needed for bead seating rather than just sealing, so yes sometimes more than one.

I’ve used 2 layers on my Pacenti CL25s, works spot on. It doesn’t really weigh anything does it?

Ah! That does make sense. If the rim bed is flat though one layer enough?

Depends on the rim and the tyre, some combinations are really tight and may only need one, some slack and need more. Not a hard and fast rule but to be fair two is probably more likely.

Generally two tends to be better for reliability, I’ve run one before and been ok, but swapping to two gave a better hold on the tyre I reckon.

2 it is then!

I did a few layers until the tyre fits on tight enough to make pumping up easier.