Advice on archival preservation needed

I have a 1940 Berkeley Buccaneer "36" print wood free flight kit which I intend to build as an R/C assist using copies of original print wood and the 24"x 36" plan sheet and preserve the original kit as is. The problem is that the 80 year old folded plan sheet (which I have carefully steam ironed flat and rolled) is to fragile to risk going through the pinch rollers at the large format copy shop. I was thinking about spray gluing (3M or Elmers) a backing sheet to the plans but have been told that it would most likely crinkle them from rubbery adhesive shrinkage. The other idea I have is to laminate the backside plan sheet to silkspan using nitrate dope.

So are there any paper preservation specialists out there with the right advice?

Download this, take to printer, print full size, good as new:

https://outerzone.co.uk/plan_details.asp?ID=5248


Or this one:

https://www.rcgroups.com/forums/showatt.php?attachmentid=6392766&d=1389050673