Congratulations, Barry. I hope your business will go well, since I know the thrill of finally starting professionally what you've been doing before as 'hobby projects'.
I started making ground glass last year as an after-hours business and I still can't give up my daytime job to live from it.
Meantime, what would your 7x17" holders cost? You can PM me if you'd rather like that. I would be interested in a lot of 5 and would eventually adapt my camera back to them if the price suits me.
I have only 2 holders now and planned to make 2 others but after 18 months I didn't start up the saw and mill to do it
Kind regards,
Geert