wow its been 3yrs since i built my top hat like retired2 design (built at same time). i have never had to empty the plastic bag on the bottom of my 50-850 which also has a baffle and large donut with 7" hole (to mount filter). i just looked at my filter and bag today ( the temp is @45 today) since its enclosed in a cabinet and its buried back in the corner (top hat is exposed) and there is less than a double handfull of fines in bag. pulled the filter off and knocked out about 1/2 a cup that has been collecting in filter for the past yr and a half. this tophat rocks thx phil and retired2 and all the others who have tweaked this system.
I'm not sure how many times I've emptied my drum since I built the top hat, but I know I will never have to empty the plastic bag under the filter in my life time. There might be a cup full of fines in there now.
I still have not invested in a Wynn filter. I probably would have done it by now if I was convinced it would make a big difference in my CFM's, but I occasionally take the Delta bag filter off, turn it inside out and vacuum it. At that point it is like a "green" bag - doesn't catch as much of the super-fines, but it doesn't put much drag on the system either.
My next shop investment is likely to be a dust extractor to replace my 40 year old J.C. Penney shop vac!