1st question is always " What do you want to carry and what do you want to do with it?" I was simply trying to get to that. You have been very vague, but asking for help. There are some professionals on this forum that have been doing this for decades (30 years for me). Answers like "I have my reasons" are not helpful for you or anyone that does this type of thing for pay, but is volunteering our services. Your title "Maximum Altitude" is not accurate as to your goals, obviously. Yes, high aspect ratio is the answer and is the most flexible as to speed range, deltas are effecient in a more limited range. Pusher is structurally problematic and a bit less efficient. There are some pusher folder spinners on Esprit Models website. That is all I have for you with the information you have provided.

Brooks the gift horse