I am with you, Joe. 300 CFM is probably not adequate for 4" dust hose and 2 1/2" will probably severely restrict the air flow.More misinformation. Or to state it more accurately, incomplete information.
300cfm under what static?? Leaf blowers are not designed to operate with any length of entering duct work or hoses, shop vacs are.
If we add 6-8 ft of 2-1/2 shop vac hose to the leaf blower how does that fan curve handle the extra static? how far do the cfms drop? 200? 100? or less? How does the added static effect the amperage draw? Does the higher amperage result in dangerous motor temps?
Also, the addition of a Thein baffle or Dust deputy further increases friction losses, lowering cfm air volume.
All of these question are impossible to answer without laboratory testing because the leaf blower is NOT intended to operate under those conditions.
Amperage draw usually drops on a blocked vac, but depending on how the motor is cooled, the lower airflow can be problem also.
Woodgears.ca has some info on measuring sp and such. Doesn't necessarily need a lab per se.
I wonder how effective a Thein baffle type separator would be with the higher air speed. Would it just blow the fine dust straight thru? Don't know the answer to that one. If you loose the air speed, you loose the cfm advantange quickly.
My main issues are
1. Large wood chips becoming high speed projectiles
2. Shop vacs are quite effective on small tools (works very well on my router table!) and not really more expensive than the leaf blower option.
I think Chris is right about the fire hazard issue. Any motor can overheat.
I just can't see the cost benefit, nor really any reduction in dust compared to a shop vac