G'day guys and thanks for your suggestions.

Marrakai: Thanks for the info, I can't find my copy of GW's book, I think it's buried in the shed in a case of books from our last move. If as your info suggests with modern powders the pressure can be kept down to 13T and still roughly equate the original spec's, it sounds like it is in the (Safe) realms of possibility. I don't have a problem with downloading if I need to, to achieve a safe load. I will not be hunting Ele's, it will probably put more holes in cardboard than anything else, with an occasional Sambar or a pig to justify it's place in the gun safe, and hopefully a buff hunt up north
in the not too distant future. I had already thought about the weight distribution and thought I would ask the gunsmith to work out a suitable profile maintaining the full 12g outer barrel dimension, then a fast taper to the muzzle, keeping most of the weight near the breech. In answer to the weight question my Ruger #1 with open sights is 9.9 pound and the only load I have shot so far is 90gr of ADI 2209 pushing a Woodleigh 570gr RN SN. That groups as good as I can shoot with open sights these days
with about a 2" group at 50 yds, standing with a tree side rest. I am thinking of fitting an peep sight and a fiber optic fore sight while waiting for the DR.

Cpt Curl: The reason for .500 x 3.25" was that I already have the cases and I was thinking that the larger case would help to keep the pressure down. But as Marrakai pointed out that is not a problem with modern powders, and it is usually the other way, with too much free space in the case. So looking at this I from that angle I will probably go back to 3".

Peter: I would be interested to hear your thoughts as to why a regulating device will work on a 9.3 x 74, but not on a .500NE. My idea was to physically beef it up a little to handle the extra recoil but if there is another problem you can see I am more than happy to listen to any advice you may have on the matter.

Thanks again all, Ian.