Steve, I had the same problem as others with the SDD and used the Oneida 5-4 reducer for a while, but am now switching to 5 inch metal duct throughout. The Fernco coupler I've got on order should work as it covers an ID range of 4.6 to 5.2 inches. Details are at the Fernco site here http://www.fernco.com/dimensional-dr...s-1060/1060-44 and you can also get them from Amazon for around $15 (although the Amazon description is wrong as you can read in the reviews)
Suggestion! I have HF DC and the SSD I am going to stack the blower directly to the input of the vacuum side of the SSD
using a 6 inch HVAC take off flange. I removed the round panel on the blower that has the 5 inch input port (suction)
I made a new cover out of 1/2 MDF used 6m x 1.0 x 16 screws to fasten the new cover. I cut a 6 inch hole with my scroll saw and attached a 6 inch HVAC take off flange to the cover plate. I have greater air velocity currently I have no way to measure the deference at this time. I will measure the current draw to see what the diffenance is from the stock set up.
with the new HVAC flange it fits snugly into the SSD, Of course foil dust tape is applied to the joints.
I will be using 5 inch HVAC (local supplier $5.50 for 5 ft ) ducting for my plenum, the drops with be with Whyes made by a local shop $30.00 for each I will have 4 drops with blast gates. I will also use a Wynne 35Anano filter in place of the bag dust distributior.:-)
My shop is a small two car garage. When I get the system completed I will post photographs.
i am currently using the stock HF blower Fan, I am at a 1900 foot mean sea level altitude in Texas I am not sure if the the Rikon 12 inch impeller is warranted.
if anyone has any suggestions please give me your feed back.