interesting links... what i'm thinking of would be a simple sort of filter with an elastic edge. just something to slip over the lip of the stack. kindof like if someone cut a piece of material into a circle and elasticized the outer edge. but, i want something that is made for this application... i spose i could make it myself but, was hoping to just find it and be done with it.
btw... my stacks are conical in form (big end receiving air) and there is no place for attachment such as a boot ring (its a curled lip) so, the attachment method will have to be what i described