hehehe Perfectionist I am
Well I tried using the industrial strength 3M tape first, but you have to cut it really thin, and trying to get it to go around the curves of the "C" sucked, so I just got a tube of Silicone, and that worked great! It was a little messy at first, but once you get the hang of it, it is pretty easy to use.
Two tips:
1. For the silicone is to use in moderation, ie don't put a lot on there, cause when you try to attach it to the car, it will have the oreo effect, and squish out of the sides, and make a big old mess.
2. Use some masking tape and a ruler, to make a nice straight line to work with on the back of your car, so you don't eyeball it, and end up with a crooked cougar on the back of your car.
I think to buy a set of new letters would cost about $15 or so (i am not sure about the price, but they charge $12 for the cougar head logo, so I can only assume that the lettering will cost you about the same), but the tube of silicone only cost like $2
Good luck no matter which way you do it
Devin