You are best off with the slp reg irrelevant of wether it has the LP Poppit or stock.
You can use an LP reg but slp will give you a slight improvement of efficiency.
If for example you had a guriella bottle you could just get the LP conversion kit for £12 I think it is.
If you try to run either the G6R or either of the victories on Hp you will get grief eventually if not straight away.
Oh and yeah that actual gat in the picture is one of ours lol. The pic was taken at Huntington beach I think and we picked it up off Left Coast while we were out in the States after that event as they do all Bob Longs custom work.
Make sure you clean under the grips after every use as they don't cover the nickel finish in the warranty and grips have been know to pull the finish away when removed if the paint is allowed to dry underneath them...