My neighbour uses flash band on the inside of the sheet and has sucess with it.
There is also the primer which gives a better bond.
The magical Flex Seal spray on liquid rubber? I think it's one of those things that sounds amazing but once you've bought it you realise it's something you rarely use. I would think it would work quite well for a temporary roof sheet repair though.Brother has seen an aerosol on FB but can’t find it now
Sounds a bit witchy pee to me but anyone seen it?
Cut one valley of a big six roof light and you might be able to slide it between the roof sheet and the purlins to shed the water onto the sheet below -assuming no fixing bolts in the way. All done from below from a cradle. Works for years.