Anybody got any idea what base/ring system will allow me to mount a scope as far forward as possible, and still retain external windage adjustment??

Have you looked at Millet they make a Angle-Loc base/rings ? They have an extension ring for mounting scopes forward the rings are also windage adjustable. I'm thinking of them for my XP.

If they make the angle lock rings that work with rail/weaver type base (and I think they do) then you can get an extended picatinny mount with the minutes built in then use the rings which can adjust for windage. First I would use one of the rail mounting systems with minutes built ni and try the posi-align and then check to see if you even need any windage adjustment.

I just checked the scope today from the prone position, and it appears i need to move the scope about a full 3" farther forward than the std. 1 piece Burris allows for (what i currently have on my XP).-- i will look at Millett-- thks.

I believe either Farrel or another Mfg. will build an extended length mount for the XP-100. I expect to hear from Ken or his wife today and I will have another mount that if it works, will be the basis to build an extended mount.