Practice on some scrap pieces first, Make some corners if you have too. Tape both sides with green or Blue painters Tape and never try to Force the blade keep just enough forward pressure to keep it in contact with the acrylic. Use the Router to smooth the Edge the blade gives you and then you can Scrape it smooth and Flame polish it.
I have never used a Plastic Blade on acrylic, on the Job we just use a plywood blade put on Backwards.