I'll start off by saying this in not approved by Parker and may void your warranty! Do this at your own risk.
Here is what I came up with for a string stopper for the Enforcer and BushWacker. I used a 4 inch bolt cut off to 3 3/4 inches. The bolt was a 5/16 x 4 and had 18 pitch threads. I put a slight bend in to get it straight with the string. As you can see it will be a little difficult to get your rope cocker hooks into the string. I should have used two bends. The rubber stoppers are from an Excalibur STS system.
You will need to remove the riser assembly to get them into the riser.
It takes about 20 minutes from start to finish. You need two bolts and nuts, a hacksaw, 1/2 inch wrench, hammer and two rubber bumpers. This will have to be a DIY project. I won't be offering them for sale. (insurance agents are funny that way) I can get the rubber bumpers for those that are interested.
I can't imagine it hurting a thing. I have a feeling all the guys putting string stoppers on the Tornado's last year prompted Parker to make them available this year. Where there is a need, someone will fill it. It's all good in my opinion, as we are getting some great products coming to market. The quality of crossbows is going to get even better as a result of all the things being done. The Cyclone is a good example, it's so much improved over last years model, it's hard to believe it came from the same roots.
I know Darton made some like that for their xbows years ago. Trying to find out if they will fit on my 2007 xbow, it's say's for 2008 and up models, but there doesn't seem to be much difference in the 2007 and 2008 models. I might have to buy them and just try them out, maybe I'll have to do some modifying.