Bigeclipse
Contributor
You are correct but I kind of disagree. Have you calculated your RMV while being frantic? I have seen friends who have RMVs of .3ish but under LARGE stress they jump to over 1. That is over triple. Secondly, recreational limits is 130ft. 19cuft at 130 feet will blow by fast with an RMV of 1. That gives just shy of 4 minutes at that depth before you drain it empty. So let's pretend for some reason you are OOA. You switch to your pony. Now you need to collect your thoughts and make a quick plan in your head. Let's say this takes you 1 minutes. That's 5cuft gone. You now have 14cuft to make a safe ascent and make a 3 minute safety stop. You will likely use 10cuft making your ascent if going 30ft/min leaving you 4cuft to make your safety stop. This was assuming you only needed 1 minute at depth. Sorry but that just doesn't cut it for me. Yes I really like 19cuft for shallower dives of say 75ft and less but anything over that and im using a 40. Just my opinion.This topic has been debated many times, to each their own. I would take the time to calculate the amount of gas needed to conservatively ascend from your deepest dives. I use a minute at depth, 30 ft/min ascent, 3 min SS, all at twice your average RMV. A 19 cf pony is what I use on all my solo dives. I sling it on the left. I have a full size SPG and leave the pony on for the dive. I could easily see if I was losing any gas. My cylinder is 1 pound negative, I take a pound off the left side. I think that covers all the usual questions regarding a pony