with regards to gel filters, I use them. On my Deardorff I put them behind the lens. That way they are not scratched or blown off. I donated a #25 to the West Coast Gods when the wind blew it right out of my hand. I now use the #23 filter. I have a type of tape that is really a glue that I press on the back of the lens board and attach the filter with that. Works like a champ.

lee