New to this, was just going by the recommended instructions for the 720 assembly. I read that IHC premier series light mikado mechs work with a bit of adjustment. Seeking any model light mikado/advice re. assembling the rocky river sar 720.
The Athearn Genesis USRA Light Mikado mech, is an excellent mech. I have used it for my 720-class and it runs beautifully. I have it coupled to a ESU Loksound decoder.
The 720-class kit has been made with the Athearn mechanism in mind. This means that some surgery of the kit "may" have to occur to get an alternate mechanism to fit. The kit also re-uses many components off the "donor" model. With that in mind, using other mikados as the "donor" may have some issues.
Potential donors are the Broadway Limited USRA light mikado which is an excellent model and as you have suggested, the IHC. Personally, I'd use the Broadway Limited way in advance to the IHC.
Good luck, the 720-class kit is a very satisfying kit to build.