Alcmaeon:  I believe the multiple (4 & 5) holes on some sporterized Krag receivers was done to mount Williams and Weaver (side-plate with detachable mount) off-set scope mounts.  The odd number holes was probably due to a mistake or earlier holes for a peep-sight.  I think it has to be a matter of trial and error to find a mount that will match up.  Scopes on a Krag have to be off-set for ejection of cases.  I have an 1898 Krag carbine that was sporterized and has four ugly tapped holes.  I intend to find a mount that matches up and use it as a sporter/shooter like you envision.