Different inlet / outlet size

[Tullochmurray]

I'm in the early stages of building. I own a Dayton motor (1/2 hp, 3450 rpm) and blower (9" impeller) assembly and have purchase the Rockler 5 micron replacement bag. I plan to stack the blower on top of a separator and exhaust it into the Rockler bag.

I have many questions and will probably answer them by trial and error - but for now: has anyone had experience with different size inlet / outlet tubes? I intend to use 4" inlet and 6" for the outlet tube. My blower has a 9" inlet. Bought a couple reducers that gets me to 6". Wanted to know if I should go to 4". Things going to get a little top heavy if I add another reducer. I could fabricate something, but at his stage I need to be sure I can overcome a number of other issues before spending a lot of time fabricating parts.

Just FYI - my other issues are: is the motor too small at 1/2 hp? Will the rockler bag work out OK? Will the blower hold up (it's rated for 1725 and the motor is 3750 - Dyton suggested "it might vibrate apart").  But I was told that the unit had been exhausting chips from a large planner for years without trouble. Guess I won't know till I plug in the first prototype.

Any feedback on the inlet / outlet diameter question is appreciated. And feel free to kick-in on any of the other issues.