Scubapro came out with the 5 port LP swivel cap late in Mk 5 production (the previous swivel caps had 2 and then 4 ports.
The 5th port does theoretically provide more flow as it is a straight shot through the flow through piston and out the end port. But in practice it makes no difference as the weak link in the system is the size of the orifice in the second stage. The flow rate out any of the ports is in excess of what the second stage can flow anyway.
As indicated above, some long hose/tech/doubles divers like the end port as it allows the long hose to be routed down along the tank with the other LP and HP hose coming off at angles that are condusive to clean configurations.
Scuabpro has retianed the 5 port swivel cap design on all their piston regulators since the Mk 5. These include the Mk 9 (which was a Mk 10 with a fixed non swiveling cap), Mk 10, Mk 15. Mk 20 and Mk 25. The Mk 18 diaphragm first stage also incorporated a very similar cap.
When you remove/rearrange hoses there are three things to keep in mind.
1. Lubricate the o-ring to prevent it from getting damaged and replace it if it looks deformed or has cuts or "feathers" on it. Ideally Christo lube should be used as a lubricant, but food grade silicone (from trident, etc) is ok for air and nitrox mixes under 40%, and in a pinch spit will work. The lubricant allows the o-ring to conform properly with the mating surface without getting stuck, torn or otherwise damaged.
2. Use a wrench to tighten the fitting, but do so vary sparingly. Scubapro refers to "tool tight" whihc means just barely snugging the plug or LP hose in the fitting, just barely beyond hand tight. It is not so much a certain very small number of degrees past hand tight but rather a feeling. Choke up on the wrench so you do not have too much leverage and stop tightening when it feels snug.
3. Older regulators like the early Mk 5 may have 3/8" HP ports. On these it is possible to put a 3/8" LP hose in a 3/8" HP fitting and the results are always spectacular when you blow up your LP hose. Due to these spectacular events the industry changed HP ports to 7/16" diameter. Your Mk 5 probably has two 7/16" ports if it has the 5 port turret, but it could be an older Mk 5 with a single 3/8" HP port that received a newer turret as an upgrade. In any case the ports are marked "HP" so don't put an LP hose in an "HP" port even if it fits.
