OK to start with your mixing up mm with cm so its probably giving people the wrong idea.

Can you get setup with 60-70mm of saddle setback and achieve KOPS without 155mm cranks?

No, but then why would you want to.

My quick and dirty calculation says that 20% of a 762mm (30") inseam puts you on 152mm cranks and while that SOUNDS like an odd size its actually quite common. MUCH more common than 155mm cranks because 152mm is 6" which was the standard for juvenile cranks and they still make that size and call it 152mm.

I was just thinking. I have JUST the bike to fit you and I picked it up cheap in a junkyard. I've spent some money fixing it up but it started life as a cheap 24" wheel mountain bike. It had a nice full diamond frame with a short reach, relaxed seat tube angle and rigid fork so I thought it was a fantastic find. I've fitted some high performance parts such as better cranks (for my use I'm using 135mm but those bikes WILL come with 152mm as standard) and I've fitted drop bars.

The thing is if you can find such a bike and spend a little money on it to set it up as a road bike you can decide for yourself if it works for you or whether I'm talking garbage. If it works you can keep it as a beater bike and build a nice custom. I really don't know of anyone selling a suitable road bike. The Trek KDR1000 with 24" wheels comes close and has 152mm cranks but its seat tube angle is WAY too steep and the head tube is VERY low. If you get a chance to ride one you should give it a go. I'm not saying that its a good fit but it will give you an idea.

To give you an idea why they build bike the way they do, ie, steep seat tube angles I think its because if you put someone on a bike with cranks that are too long for them they have a lot of trouble getting over the top dead centre position if they are seated at KOPS. If you move them forward of KOPS it opens up their leg angles making it easier to pedal over top dead centre but at the expense of putting too much weight on the riders hands/shoulders. Its a quick and dirty fix and its all the bike manufacturers are prepared to offer at this point in time.

I know I'm giving advise out of left field but thats all I can do at the moment. I'll try and take some pictures of my 24" mountain roadie tomorrow. I think that where you need to go next is to get yourself a 24" mountain bike beater and see. They unfortunately aren't all the same. Many of them have seat tube angles that are too steep too so use your eye to look for one with a relaxed seat tube angle.

Anthony