Very interesting project. Nice to see something different.

"...A 30oz. thrust would probably do the trick. What is out there that might fit the bill? ..."

I don't know anything about the GWS75's. If it were me I'd use two MF480's, driven by HET typhoon 2W BL motors and 3S lipo's. With the simple ducting shown, that combination will deliver at least 17 oz per side.

Keep up the good work.