I would have to disagree with Hepa bags being detrimental only because using the new Hepa style Air-Tec bags in any and all of my Air-Ways increases the air flow significantly.
Some here have also taken one of the Kirby Filtrete type bags cut, sewed it to make a type C bag for a Hoover Convertable and it also increased air flow and cleaning performance.
The Hepa bags actually may be a finer webbed design, but it is done in such a way that allows for more service area that is not clogged thus not restricting air flow. Even Oreck now has a great bag that is also is charcol lined preventing many oders.
I have completely filled an Air-Tec bag in my new Air-Way, plaster dust, fine sawdust and construction dust, same with the Miele, while cleaning at the church after the restoration, and there was no noticable reduction in air flow.
Just my opinion, but I think it would greatly increase bag life and possibly air flow even in older Lux models. If so, it would also keep the motors cooler as air flow would not be deminished. I am willing to give it a try. Not sure however what effect it may have on the full bag mechanism on the machines.
Morgan