I hoping you would leave me out of this...
so, let's try this again, for the benefit of the readership...
I'm more into doing it right the 1st time and not spending more till I get where I could have been to start with for less... (penny wise pound foolish theory)
the additional cost of upgrade and modification: (IMO is throwing good money after bad)...
2nd HF DC for parts.. (hmmmm)
canister filters..
external 4'' separator.. (which reduces CFM as does El's , flex and lengths of run collectively)
all of the additional cost of upgrade and modification puts you very closely in the price realm of a much superior and better made plug and play DC unit that is way quieter, (±65db) already has a canister filter w/ cleaner, doesn't redistribute dust, has a higher IRL CFM rating, and will be trouble free for a very long time.... VOE...
the inlet on the HF is 4''... and you simply can't pull their unrealistic rating of 1600CFM through a 4'' hole.. you can't do it...
no matter what impeller or motor you put behind it the 4'' inlet is only going to allow ± 350 CFM..
more motor and/or impeller will make a real screamer out it of though... HEY!!! Looky here we gots us our own jet engine sound effects...
also, cleaning the filter on the HF is one seriously messy job... you said yourself that you needed to take your's outside to clean it... that has got to be a pain
installing the DC outdoors like you did will run up your shop heating/cooling cost...
the better unit will be either a 5 or 6'' inlet which translates to ± 550~780 CFM...
I used the Jet 650VX DC (but you often brought the cost of a Jet 1100 which I have into it) as a base line comparison but there are many other brands out there comparable to the Jet 650...
