the 'minimum' thrust to weight ratio would be that to maintain an air speed greater then the stall speed of your wing(s) with what ever drag your craft creates at that speed in the air or the thrust needed to accelerate to that speed (on the ground/air/etc) and then a bit more so you have climbing ability.
I know that that can be less then 1:1 thrust to weight for real aircraft.
a glider's WCL is under 4, so lets use that for a target and 10lb AUW given the numbers you have given already. (which would be thrust:weight of 0.25:1)
gliders have an aspect ratio of 8-12:1
a 10ft x 1ft wing (10:1 aspect ratio) runs a WCL of 5.1
a 10ft x 1.5ft wing (6.67 aspect ratio) runs a WCL of 2.8
a 12ft x1ft wing (12:1 aspect ratio) runs a WCL of 3.8
(also for drag/lift, I think a wider wing is better, but 10ft is already going to be creating structural challenges)
a 10ft x 15in (easy math range for the above measurements) would be 6 sheets of DTFB + your wing spar @ 120g each => is 1.58lb if you don't take off the internal paper (which would probably be a good idea) and then you still need the spar. So the 10lb range looks at least theoretically achievable based on your stated numbers.
a quick google gives this
RC cars australia: which shows a 747 at a thrust to weight of 0.27:1. so you might need a bit better then 0.25:1 that we came up with before, but at least puts us at a 'theoretically' possible level based on actually flying aircraft.
if I was going to try this, i would look at a 12ft x 1ft wing with a carbon fiber rod reinforced spar (probably 2 light spars separated by foam vertically) with an appropate airfoil shape (look at some of the smooth curve wings over the FT standard angled one). you would also need a big runway to get up to speed.