My circuit is very similar to bootstrapped mode schematics,except few changes:
1)bigger inductor-47 uH,should be capable of handling up to 2.5A.
2)Rsense - 20 mOhm (milli)5W.Don't use smaller than this,I tried first with 10mOhm,and blown the MOSFET.This brought me to use more powerful MOSFET,that can handle about 3A.Don't forget the heatsink!
If I remember correct,I get about 1.5A using 5v input,and about 2A with 12v input.But when I was approaching to 14-15V (simulating car voltage when engine is running),the MOSFET became VERY hot,and I was afraid it will blow while using for a long time.So I decided to stay with 5v input.
Why do you need so much current at 12v? If so,I think using flyback transformer would be better and more efficient.Using MAX1771 seems like using an inverter: like converting to 220v from 12v and then back to 12v,it is converting 12v to 5v and then back to 12v.And also,you wanna use 2 MAX787 and 4 Max1771,with coils,MOSFETS,and big heatsink...that's pretty many parts for 12v line!I think it will be cheaper and more efficient to double or even triple Sproggy's 12v section from his PSU.