ive been thinking about getting ft boots for the upcoming season and was wondering what the flexes would be comparable to a 100 - 110 flex boot so any advice would be greatly appreciated
As someone earlier noted, the liners themselves add to the boot's overall stiffness too, so if you put a #10 tongue on a Classic, it won't be quite as stiff as an out of the box Seth boot because the liner of the Seth is way stiffer and firmer. Bear in mind that the whole point of FT's 3-piece design is to provide an unimpeded flex pattern, so a #10/140 tongue might feel softer only because it's actually flexing the way it should.
Your a little off in your conversion there. A 10 is no where near a140. Take about 20 off all those and your about right. But to op yeah full tilts are pretty soft and often need the shells riveting to stiffen them up.