As the sitting position in the car is quite reclined, standard seats available from Demon tweeks and/or others just don’t really fit! To this end there are two main options, an expanding foam seat or a ‘bead seat’. I have plumped for a bead seat as the beads are all contained within the bag, this should help stop some of the mess, and gives you the chance to have a couple of goes before adding the resin to the bag. You also don’t get a weal seem where you pour subsequent layers of foam into the bags, which you shouldn’t really do anyway. The only drawback is that a beadseat costs more than a tin of expanding foam, but hopefully will produce a better final product.