I have a part from which I want to take a mould - it's around 50cm long by 46cm wide at the widest point.  I'm unsure as to whether the ready mixed epoxy fibre kit would be best or the uni mould kit, and which size to use if the former.  Guidance on this would be great.

It's a small motorcycle fairing and is curved so part of it touches the board and the top is about 6 inches of the board.  I've watched the video and saw that when making a small part, modelling clay is used to created flanges. I could do that with the part it would just need a fair amount of it (46cm across by about 15cm high) to bring the moulding cloth/putty down to the board. Is that the best thing to do? Or better to cut out sign board and make flanges that way?