Clever idea But ... 200 mm is barely adequate for many 1/35 models. I measured the diagonal of the Merkava Mk 3D (early) by Meng and the result was about 230 mm. The area where the track touches the "ground" will probably fit inside a 200 mm circle and the rest will overhang the base (the barrel will obviously stick out a lot). An M109 (witout barrel of course) will fit, the A6 version will overhang a little due to the boxes at the rear of the turret. Translated to 1:1 the 1/35 patches represent a 7 metre (or almost 23 feet) circle which can hold a 2.5x6.5 or 3x6.3 metre (8.2x21 or 9.8x20.7 feet) rectangle. I would humbly suggest oblong patches or offering them in smaller and larger sizes for 1:35. The 200 mm is slightly large for the smaller stuff (like a Pz IV or Sherman) and gets crowded with Tiger II and most modern tanks. Then there is the minor detail of getting something in the right size to glue these on / Robin

Nicely put, I agree with what RN said