OK, you could buy one of IP's roof jigs... but a cheaper way is to 'form' it over a hot radiator.
This is the result:
I usually use ply to roof these coaches but because I'd run out of suitable material, I had to use the plastic supplied with the kit. When using ply, I steam the wood and form the curve so I did the same thing with the plastic (except that because plastic is non-porous, I had to use direct heat.)
Works a treat! (but only in winter.. putting the heating on in summer just to form a bit of plastic is a bit OTT)
This is the result:

I usually use ply to roof these coaches but because I'd run out of suitable material, I had to use the plastic supplied with the kit. When using ply, I steam the wood and form the curve so I did the same thing with the plastic (except that because plastic is non-porous, I had to use direct heat.)
Works a treat! (but only in winter.. putting the heating on in summer just to form a bit of plastic is a bit OTT)