I am really thinking about reverting all the threads of the project to NPTF. The CGA320 adapter is 1/4 NPTF, the Wizard of NOS SPRV is 1/8 NPTF, the gauge that I will have to use on RFL events is 1/8 NPTF and the dump valve looks like is going to be 1/8 or 1/4 NPTF also...

The Dump valve will probably be savaged from a Paintball refilling station that I bought last year, the valve is pretty small 51 x 28 x 48 and can handle 65BAR, one alternative is to use a NPTF 1/4 Male to G1/8 female adaptor from Burnet and Hillman to convert it.

The other dump valves options are:

-Parker MB or B PR Series (with compression fitting tubes):
http://www.fluidcontrols.co.uk/valves/ball-valves
-Aerohydraulics 1/8BSPP High Pressure (I don't have any information about size or weight, but there is G1/8 option):
http://www.aeroindustrialproducts.co..._p-99-438.html
-Legris 4730 - 2way Female BSPP Thread G1/8 100BAR - 4730 04 10 22 (A bit heavy... 350g):
http://legris-autoline.com/Legris_ec...hoisis=1_G1/8@
-Mars One Piece Reduced Bore Stainless steel Ball Valve G1/4 (Only 70g and as small as the aforementioned paintball refilling station):
http://www.valves-online.co.uk/acata...all-Valve.html

Today three CGA 320 to 1/4 NPTF adaptors, one anti-syphon tube (the main tank will be almost horizontal to keep height low) and two paintball on-off valves and the 1500 PSI dye gauge arrived. Just waiting for the two 16oz bottles from Pure Energy (75 x 205mm).

The paintball on-off valves from JustPaintBall.co.uk have a smaller bore than I thought, maybe this will be useful to prevent bottle freezing, although I will search for other alternatives, any suggestions?

Cheers,
Eduardo