- Welcome to the forums. When you get a chance, please update your profile with at least, a first name.
Just so we're all on the same page:
A flush trim bit has the bearing at the end of the bit, furthest away from the shank
A pattern bit has the bearing between the shank and the cutter.
You said you were using a flush trim bit with the bearing at the top. Does this mean your router was in a table "with the bearing at the top"?
You also said your template has some rounded inside corners - were you routing both inside and outside edges?
Routing direction is important: if your router is in a table, when you router inside edges, the bit travels in a counter-clockwise direction. For outside edges, the bit travels in a clockwise direction. When hand held, it's the opposite. Tough to explain in words, but I'm sure Stick will be here soon to add some pictures.
So, was your router in a table or hand held?
Were you routing in the right direction?
You also indicated that you rough cut to 1/8 to 1/4 inch and were using a bit with a 1/4" shank. Perhaps 1/4" was too much material to route. A 1/2" shank would be much better.
I can't advise on the tape you used as I've never used it. If I can I tack my templates down to the work piece with a pin nailer, in an area that isn't conspicous.