Hey Max,
Hope you did not take it as a flame.. Sorry about that. I love the fabric molding idea. That was totally new to me.
The mat glass will probably have the very same price, and might even cover a larger area, and will certainly have a cleaner appearance, and less little nasty pointing things to grab you and rip up your gear. also easy to wet out. It all good.

Mat is great when you want to add bulk to stuff.
I had a friend that had a family business building yachts. On one of the days they were laying up a large hull (50 foot I think) he poured the polyester resin into a large 5 gallon bucket, and added catalyst, then his dad came over and added catalyst, and then his uncle... Seems about 4 guys came by and added catalyst to the bucket no knowing the other guys had. The last guy picked up the bucket to drag it over to the work area and noticed it was starting to kick off.. Then he noticed it was getting hotter... About this time he dropped it, and poof. Sor the story goes. I tried to duplicate it with a small amount of resin, and it just got really hot, and melted the mixing cup.
Hot batching to limits is fine. But if you have a 1 hour set time for a resin on a fender project, that is probably about right.
I guess I should mention, DO use disposable gloves with this shit, and try to have a lot of fresh air blowing around. You will want to have gloves as this can get to be pretty messy job, and as the resin starts setting up, you will probably have some shit sticking to you that you don't want sticking to you.
I just recommend you avoid S-glass if you can. I hate that itchy shit!
My background is simply hobby relate stuff. Started building R/C airplanes in my own molds and the such. Then assisted a friend that was building a 2 place plane from carbon, kevlar and glass with epoxy resins. We did some nice big layups on that one!
-Wayne