The same question has been asked on one of the longrifle sites. These kits are actually a pretty good place to start, the barrels are accurate, the percussion locks are OK, flintlocks not so good. You can slap it together and shoot it or you can study how a Hawken is supposed to look, remove some wood and have a really nice looking rifle.
My answers on the other site was first; don't use a dremel tool on your build, it can get away from you in a heartbeat and really mess things up.
Next; these kits come with a lot of extra wood particularly around the lock. Big lock panels look awful to anyone who has seen the way they are supposed to look. The forend in these kits is what we call "slabsided" (flat) and doesn't look anything like an original which has a more oval shape.
Here is an example of a big, ugly, lock panel;
An original Samuel Hawkens lock panels look like this, a very distinctive shaped tail and nose, graceful;
TCs lock panels are smaller but can still be reduced to a more pleasing shape like I did on this Renegade;