One of the easiest/best methods on the transfer of larger images comes from the training I got as a sign painter. It's the method, I understand, that came by way of Michaelangelo as recorded in his procedures of transferring images for the work at the Sistine Chapel. It's called a Pounce Pattern.
A pounce pattern is when you make perforations in paper by pressing into the paper a small pointed wheel (or an "Electro-pounce" which burns tiny holes in the paper) around the outlines of your image. You then take the paper image full of tiny holes and tape it to your substrate and bounce and rub powdered charcoal in a cloth bag, through the holes onto the area. You take the paper away....voila!....nice dotted outlines for you to spray fixative or redraw in permanent sepia pen. You can make registration marks from where you taped the paper and go back and re-pounce if necessary.
To make the best undistorted pouce patterns on the planet...is to print them out on your printer. You can blow up your image to any size you want....even a billboard size.....and "tile" the pages together and your in business.
Dick Blick, whom we all know and love, has been an excellent provider of sign making materials since day one.
Here's there page on pounce wheels.....
http://www.dickblick.com/zz289/11/pr...m=0&ig_id=2724
And pounce powder and a nifty pad they sell. (in lieu of just wadding up a pile of powder in a rag and tying it off)
http://www.dickblick.com/zz289/10/pr...m=0&ig_id=2720
Blick used to sell the Electro Pounce...but I couldn't find it on their site....so here's what it looks like -
http://www.pacificcoastsignsupply.com/catalog/pg_75.htm
-Gear