Thanks for your help Viper, it's more clear now!

Here is why I needed it: A small plane like that should have a wing loading (oz/pi2) ratio between 24-27 oz/pi2 for maximum performance (a friend told me that). With 855 in2 area and 11 lbs weight (MVVS1.6 on the nose!) , I would have 29oz/pi2 ratio a little bit too heavy...

If I can reduce the flying weight to 10 lbs max, I would have a 26.9 oz/pi2 ratio and better flight performance for aerobatics

That's why glow engine is better on that plane but I want to put a gaz engine in mine to fly a lot, at low cost To get it, I will have to reduce the plane's weight with an heavier engine like gaz.

Have you already done some similar calculations before? If yes, what would be the wing loading or the oz/pi2 ratio on a similar plane?
I am just a backyard engineer trying to understand how planes fly!!