""on a plane weighing 23 pounds""

rcm243,, have you yet flown the G38 on this plane at that weight ??
I had a G38 in my 15& 1/2 pound Miss Los Angeles and I was not happy at all (but that was me), I needed more power,,
I have seen a 19 pound Steersmen fly with a G38 and it needed practically full throttle just to stay in the air, yes maybe a better pick of prop would have helped but still it needed more power,,

as for a prop on my G38 I used a 3W brand 19x8, it had a length of 18& 5/8 inches, I got 7000 RPMs tuned for flight,,
most posts I have read people use a lower quality brand 18/8, 18/10 on their G38s and get 8000 +, even up to 8800,, but for a 23 pound plane I would suggest something like a 20x4, 20x5 (if you could get one) so your Engine would pull better at half throttle "that is if you could get a good RPMs out of a prop with a 20 inch length" so you wouldn't need full throttle just to keep it in the air,,

now I know there are guys on here that will tell you diff, but that is my experience with the G38,, my advice, is, at 24 pounds sell that G38 and buy a DL 50 (sorry G38 lovers !!)..

edit,
by the way, other than being low on power by today's standards my G38 started very very easy, with just a tiny bit of a flip, and it was very easy to tune and it ran flawless !!

hope I have helped !!
Jim