I am new to diving and want to purchase a good HP steel tank that will make it easy for me to stay under a while or do two short dives. I have been reading that the OMS 131 would be good and can even get 175 cui at 3500 psi, but I was reading that Faber has a new 152( I believe) that might be nice. What is the best tank for me to get to hold the most air? Will I have a problem getting my local dive shop to fill a HP up to 4000 psi? Should I wait until I can find a pair of say used 110's? Please help me because I don't want to make the wrong decision here. Thanks, Bob