It could be more efficient if you use a old cardboard boxes and duct tape to build a custom fit shroud connecting/ mounting the filter to the fan.
I use a similar setup on a homemade glove box / flow hood type device for culturing mushrooms. I have an 8" duct booster fan pushing air into a cardboard box. Between that box and the flow hood I have a HEPA filter sandwiched between them using bolts and wing nuts. The only thing I'd change is the fan. The booster fan was cheap, but has trouble with the back pressure (lower air flow). I would probably look at using squirrel cage or maybe a radon fan. They should be able to handle the pressure.
I use a similar setup on a homemade glove box / flow hood type device for culturing mushrooms. I have an 8" duct booster fan pushing air into a cardboard box. Between that box and the flow hood I have a HEPA filter sandwiched between them using bolts and wing nuts. The only thing I'd change is the fan. The booster fan was cheap, but has trouble with the back pressure (lower air flow). I would probably look at using squirrel cage or maybe a radon fan. They should be able to handle the pressure.