Daystate Huntsman Regal HuMa regulators are now available - these will only work on the newer models with a 2 piece hammer tube/air cylinder, not the older one piece models. It does not involve drilling a breather hole in the air cylinder like some other regulators do, the regulator is vented so you don't need to worry about the regulator pressurising itself and locking up the way un-vented regulators do.
These can be DIY fitted. This video shows you what is involved in fitting a HuMa regulator to a Regal https://youtu.be/S6Lxp6lhYjU
Have a look in the eShop for prices and availability.
I can order new rifles, spare parts and accessories from Daystate if required.
For user manuals and user guides have a look >here<