AIUI there are no magic principles associated with the guidence on the number of controls on a route; they are simply pragmatic.
If controls are more then 60~70km apart then folk start worrying about riders jumping on a train, whilst if there are too many then (for traditional calendar/perm events with manual validation/brevidence) neither the validators or riders would wear it.
But such factors are irrelevant for GPS DIY perms for which validation is largely an automated process wherein the only manual component is for the validator to confirm that yes the track does goe thru the controls, and that can be acheived simply by glancing at a map of the GPX showing track and controls, as supported by most every mapping app/website available (and even that down the line will be automated; it's only a matter of time).
As for magic numbers, four per hundred km sounds fine, except the Tour of The Hills 110km calendar event for example has about 10. Was not the fact that DIY GPS can support additional controls necessary for wilder/hilly routes one of the major arguements put forward for their acceptence?
So there are no magic principles and magic numbers are arbitrary, introducing as many problems as they solve.
As noted above GPS DIY riders who specify controls without due consideration are only making problems for themselves but thats their problem. That definately seems like a 'pragmatic principle' which should be documented in the guidelines provided.
I don't believe the approach described above is inconsistent with current practice, or to put it another way, to reject this approach will require more regulation, not less.
Let's solve the larger problem.
