"aluminum" and "stainless" are @ as generic of terms as saying that we keep "tropical fish". Their are many different grades and for stainless the metallurgical differences are very vast( some has a lot of chrome or is magnetic. Back to the subject, it would be easier, safer and would take less time and probably no more money to go and pick up a nice piece of acrylic that you can see through and cut out pockets for your filter return, air line,heater etc. If you choose to go that route, I can help you with how to prep and set it up so you don't crack the acrylic while cutting it( I have 15+ years machining and cutting everything from woods, plastics, stainless and tool steels so I am more than knowledgeable in how you could do this yourself).
