The Sherwood Gemini is a great piece of gear. It has a heavy cracking pressure out of the box, something your LDS tec can tune down if you like. Once you break the cracking pressure though you get plenty of air. I've used it personally when I bought my first set of gear. It inflates faster than a normal inflator, something I've found all integrated-octo inflators do. Just for simplicities sake, I'll be calling all integrated-octos Air 2's.
There are several things you must consider if using an Air 2.
1) You'll be donating your primary and using your Air 2 in an Out-of-Air (OOA) situation. Because of this you should have a long primary hose. Having to share air with the short standard 28in primary hose gets very claustrophobic and often makes it hard for either diver to manipulate their gear without getting in each other's way. For this reason I recommend getting a 40in primary hose at minimum. You can also get lengths of 5,6,7, & 9 ft; but that requires a different set of training as you'll be wrapping the hose around you in a specific way, and deploying it in a specific technique.
If you get a 40in primary hose, you should also get an angle adapter or a swivel so you can keep the long hose under your arm, instead of bowing out to your side.
2) Air 2's use a different style of inflator hose compared to the normal inflators. This means you cannot mix and match your BC and reg with other BC and regs unless they use an Air 2 as well. The hose they use has a bit more girth and allows for more air flow.
3) Because of the wide inflator hose, you can breath out of your Air 2 just fine. But your BC can also inflate faster as a result.
4) When sharing Air, you'll need to choose a correct technique to dumping air on ascent. I would advise against taking the Air 2 out of your mouth to dump, there are safer techniques. I can go into an explanation if you would like.
5) For safety reasons, you should not tie down your Air 2. This could hamper your ability to quickly dump air and/or deploy your Air 2 for yourself.
Personally, I did switch out my Gemini because having an Air 2 didn't fit with my style of diving. I found that I was unable to tie down my inflator for safety reasons. Some of the diving I do requires me to be right down next to the ground and my Gemini as a result would scrap the bottom.
Other conflicts I had were as follows:
- My BC corrugated hose was stiff, and tended to push my Air 2 out of my mouth.
- Because it dragged, there was always the possibility of sand causing the Air 2 to get gunked up or have one of the buttons jam
