Stop in for a cup of coffee

hmm so the outlet from my little tank is 3/4 npt as well, so with that in mind, think itd be better to just run a straight 3/4 npt to the bigger tank? Seems to me that going from 3/4 to 1.5 back to 3/4 would be kind of pointless?
I think there is some gain in still going bigger on the pipe. Every elbow is a restriction, but we don't upsize at the elbows to keep it all even...So, maybe 1" to reduce that factor. On the other hand, I would ask what you are doing with it. If you are not using that much air it might not matter. A couple tools on 3/8 air hoses are going to be fine on a 3/4 feed. Of course that could make a case for whether you need extra storage at all. Will the compressor keep up with whatever you are doing? The extra storage is just allowing you to build air in the off time when tools are not drawing it as fast as compressor pumps it out. Also, watch the MAWP ratings on tanks!