Think it would be to much hassle fitting a reg because of the layout of the air cylinders it would be a lot of work positioning the regulator and don't think it would be cheap but it can be done but to be fair they are ok as they are they have a good shotcount they are consistent and they also don't have a massive power curve like earlier Turkish guns they really are getting their and you can't really fault them for the price,
They are also very good at Fac levels I tuned one to 25ftb it shoots well and has a good shot count around 60 that's pritty good for an unregged fac pcp.

Dave.