Polo Bikes

I'm 6 ft 2", and I've basically shortened and steepened what I have (XL Pompino) but used 26 x 1.25" tyres whilst trying to preserve the same riding position and leave enough room to go to 2" tyres if I want.

Your design doesn't fit 2" tyres unless you plan on having a curvy seat tube or something? The trade offs by designing for two different tyre sizes are too big in my opinion (you can't have an ideal rear end/front centre/BB height/trail/wheelbase/etc when designing for both), I'd pick one tyre size (or a middle ground) and go from there?