Registration Issues

I am in the process of purchasing a few large rolls of film from Ilford for some specific projects in mind.

I have a few questions/observations that I would like to put forth.

I am not sure who to credit but I saw here.. someone is changing the size of negatives to reflect the shrinkage in paper. This at first seems to me a very practical way of approaching registration issues with multiple coats.

My question is this... if the paper has grain going in one direction I imagine that the shrinkage is greator or less going with the grain . or simply not *linear* (not sure if this is correct term)
But when you reduce the size of the film in lets say a % factor the ratio is kept. Therefore I would imagine that on lets say a 30-40 inch image if you got the one direction matched, I think the other may not be a perfect match. Causing a mis-registration???????

Another ques or observation... If one used a very thick paper stock and mounted the paper to a very rigid stock using a quality mount material,,, I am thinking aluminum which is thin enough to be punched.. Would not the shrinkage be minimised???
One would then need only to strip, or peel the paper from the support??

I have not tried either of these methods, but since I will be spending a few years on paticular projects in large print size , I am curious of your thoughts.

I have done countless multiple registrations images on 16x20 E6 films in the past , in fact too many. Registration was never an issue as all work was done first before the emulsion ever hit a chemical or wash.

Any thougths or comments on this subject would be appreciated.