Filling, fitting and pinning are the most problematic. There are some that require alot of test fitting. On these large kits a set of small files or even a Dremel moto tool is a must for shaping and fitting. This particular kit above had a good fit but required filling of some air bubbles. You get that alot with the resin kits. Now vinyl kits, I tend to stay away from them because finding something to adhere the pieces together is problematic. I have done one vinyl kit and ended up using a product called Goop on it along with sanding prior to application of the glue and then filling of the parts with plaster. The vinyl kits are hollow and so the pieces don't have alot of surface area to adhere to each other, sort of like a large vaccuform kit.