OK RT the technique I spoke of would work well on your lovely Pitts S-1. What you need to do is assemble the airplane with both wings and with the larger airplanes such as this one its easiest to work with someone else. The idea is to stand the airplane on its nose with you helper holding it near vertical.

Now you step back around fifteen feet or so. The idea is to get your eyeline perpendicular to the airplane and looking as if you were above the airplane and the wing outline you will now see is the projected planform as well as the collective outline of both wings. from this perspective it will become easy to visualize just where 25% or the quarter cord is by a visual estimate. With just a bit of practice you will be amazed how easy it is to imagine where that point is and what I recommend is to practice this technique on any of your other airplanes the easy ones with straight cord and the taper wings as well as swept.

Is this precise aero engineering - Certainly not but is a method you can practice and actually amaze yourself with a little effort.
Now visualizing that one quarter point (25% MAC) is of course not the perfect CG perhaps for every airplane but for the majority of types we fly it is a very practicle and safe starting point for much of what we fly. Likely you pitts will ultimately be best at around 28% but always start a little forward than aft and you can adjust CG to how the airplane flys from your safe starting point,

Just yesterday one of the fellows presented me with I guess what would be considered a sixty size and it was an unknown bipane he had refurbished it only took minutes to step back and pick out that quarter cord. After taping on an eight inch cresent wrench to the top of the cowl to adjust to that point the airplane flew quite solid and graceful with no suprises.

I know this is no fancy computer project but it has worked very well over the years as a quick and satisfactory method for all those 'mystery airplanes' and its well worth learning as one of those useful tools.

John