I think a skinny-winged U-2 would work if you put a thin carbon-fibre reinforcing spar epoxied to the wing to stiffen it.
Your motor does not look like a high-average thrust, so it would work.
I bet you could easily quadruple those glide times with a U-2 'like' design.

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When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !