Hi
I have made up inner wheel wells using flat premoulded sheets of fibreglass cut to shape and then bonded in and further strengthened using more mat and resin.
The sheets of flat laid up fibreglass were bought from a local fibreglass moulding company, I used the smooth mould release face on the wheel side to help keeping them clean from road debris etc, the chopped matt finish facing the engine side as this was the covered in heat reflective mat.
cheers,
John.