I'd add a +1 to getting another 100 cu.ft.
Your profile says 0-24 dives. When you are first learning to dive you will move your arms too much. You might be overweighted and finning too much. Bottom line, when you learn to have good buoyancy control and become a better diver you will, hopefully, find your 100 cu.ft. tank is lasting you over an hour at 45 ft.. I remember leaving the water because I ran out of air. Now I leave the water because I've hit my NDL. I usually have 30+ cu.ft. left in my tank when I hit NDL.
I have four HP100 tanks and one HP119. The HP100 is 7.25" diameter. The HP119 is 8.00" diameter. Changing my straps on my harness is a pain. Once I stopped needing 100 cu.ft. of air, I quit using the HP119. So if the larger tank is an 8.00" diameter. Don't do it. Get another 100 cu.ft.
Also, make sure they are the same manufacturer and model. Not all 100 cu.ft. tanks are built the same.
Darrell
Your profile says 0-24 dives. When you are first learning to dive you will move your arms too much. You might be overweighted and finning too much. Bottom line, when you learn to have good buoyancy control and become a better diver you will, hopefully, find your 100 cu.ft. tank is lasting you over an hour at 45 ft.. I remember leaving the water because I ran out of air. Now I leave the water because I've hit my NDL. I usually have 30+ cu.ft. left in my tank when I hit NDL.
I have four HP100 tanks and one HP119. The HP100 is 7.25" diameter. The HP119 is 8.00" diameter. Changing my straps on my harness is a pain. Once I stopped needing 100 cu.ft. of air, I quit using the HP119. So if the larger tank is an 8.00" diameter. Don't do it. Get another 100 cu.ft.
Also, make sure they are the same manufacturer and model. Not all 100 cu.ft. tanks are built the same.
Darrell
