Bob I believe the reason the quarter cord seems more to the rear when you look at it as I described is because you are looking at the collective outline of both wings and not just one wing that we are so used to and for these purposes the collective outline is what we need to base our estimates on.

Now with your straight bottom wing and with that swept top wing of 10 degrees that means the trailing edge of your collective view is going to be straight and the leading edge is going to have just a bit of a bump in the middle. If that leading edge were you to imagine was straight from the tips its very easy to estimate the quarter cord using that view from afar as I described (practice, practice) and then just allow the point just a smidge further forward because that area forward in that 'bump'.

Agine practice, on you own airplanes even better your buddies airplanes That are know good flying airplanes. Stand 'em on their noses get way back and note your estimate of what you think 25% is. Then just check the airplanes in your fingers and see where they are actually flying them at. Yes some will be just a bit further aft than the quarter cord and that's fine but what we are looking for is a known safe place to start with. Of course fine tuning later can be move aft a bit but on that pitts you really want that 25%.

John