OK, I was assuming 10in chord, but you are using 12 in chord, which is a good thing. However, your takeoff speed is quite a bit higher than is realistic. Hopefully with flaps & a higher CL, it would be even lower.

If the airplane weighs 30 lb, Cl is 2.0, and the wing area you provide, the stall speed will only be about 11.6 m/s. So takeoff speed would be around 13 m/s resulting in your Re of 270k. Not as low as I first thought, but still lower than the 300k data you would like to depend on. Anyway, if you add high lift devices, the basic airfoil data becomes part of the background and not quite as important as before.

I like the wing Aspect ratio and non-tapered design you have in mind.

Never heard of the LI74.....