Mike, have a look at Ralph Lambrecht's site. He gives instructions to make a test strip printer which takes 5x7 paper and either does 7 one inch strips across the whole neg or easily allows you to do 7 strips of the same part of the neg which the Paterson will do but only 5 and more awkwardly.
It shouldn't be so hard to work out the dimensions to make the space for the test paper become 8x10 instead of 5x7.
I use Ralph's test strip printer on a regular basis. It really is a useful piece of kit. Actually I think the design is down to his partner Chris Woodhouse to give the credit where it belongs
pentaxuser