Thank you for the suggestion. Nope not too late. How much would you suggest? 1/8"

Can't say I know the model, but if it's Pee Wee powered I guess it's about 30 to 36in span?
I should think 1/8th would be about right as a starter. But you must remember EXACTLY how much downthrust or sidethrust too, for that matter depends on a lot of things.
Start off with the 1/8th or a fraction less and see how it goes, then add washers where ever if need be.
Good luck.