Very Informative as always!
so you’re telling me that all else equal, stock size tires will give me the extra speed on the top end??
No...
Correct gearing will give you the best actual results. You can compensate, just takes a little math. Slap a measuring tape around the tire crown, I can take it from there. If the difference is, say, 11% we'd just need to figure out a sprocket combo that's ~5% shorter than stock, to get an
effective final drive ratio that's 6% taller than stock. IOW, crankshaft revs per mile need to be within a narrow range.
What you can't change is the speedo input error. A mechanical speedo drive is geared for one size tire...i.e. revs per mile and can't be changed.
All of that having been said, returning to stock Trailwings...or another tire with the same rolling circumference...would restore the original speedometer input (IOW, it'd read the same as it did with the `Wings mounted) and, you'd simply run the original sized wheel sprocket and a 16t C/S sprocket. That'd remove not only any guesswork, you could leave the calculator alone. That's a known combo.
The hardcore math...stock gearing for any of these bikes is ~4.77mph/1000rpm, in top gear. An 88cc (52mm bore) makes enough torque to pull up to ~5.05mph/1000rpm. You now have somewhere between 5.49 - 5.68mph/1000rpm. The numeric differences might seem small, they aren't. Small-displacement and limited torque engines need to be able to rev to make full power. I'm guessing that your tune should reach its peak in the 9000-10000rpm range and not really fall-off until closer to 11,000rpm.
44mph, as you're now geared, takes ~7800rpm...if the speedometer is close. Bone-stock, a CT70 engine doesn't peak until 8000rpm, and that's a 3-speed; the 4-speeds can rev beyond 10,000. If gearing is holding the revs down below 8000rpm, the engine is being overloaded. The awful part of this is that we don't really know if that's an accurate indicated speed, nor how far it differs with those big shoes on the bike. You could, conceivably, be topping-out at 48-50mph with the engine revving closer to 8700rpm...which is still too low to let it reach its full potential. Multiple variables make this a guessing game. 88cc can make decent power but everything, including the final drive gearing must be dialed-in, there's not much room for error.