I've been looking over various plans and images of plans on the 'Net (Google Images has all sorts of interesting tidbits, but a lot from model aircraft). Obviously any older plans or US-originating plans are going to be in inches & feet rather than mm/cm/m. If you need to source spruce (or say Qld hoop), or metal tubing and the plans all call for 1", 1.5", 2", 2.25:" etc. etc, do you buy and cut wood down to plan specified size or just oversize when it comes to metal? Even the EAA table is all specced in inches and feet - http://www.eaa1000.av.org/technicl/worktabl/tablefig.htm
For those interested in looking at plans, I've also discovered the Aircorps Aviation Library which has some free images of WW2-era plans.
Tim