Brian
Good point about the size of the dust bags on fan-first uprights. However, there's a disadvantage to that - poor suction & airflow. Go ahead & open up your Hoover & see the fan on it, the fans on these 8 lb cleaners are pathetically small, they really don't produce much airflow to properly clean with. The one exception being the Tacony 8 lb uprights, those do have a proper fan in them. These 8 lb uprights rely primarily on the cleaner's brushroll to do the majority of the work.
The other major disadvantage with fan-first cleaners, the ones where the fan is mounted to one side, motor pulley on the other side & dirt tube on the side, is even when using HEPA Cloth bags the suction & airflow drop off really quick with hardly any dirt in the bag. Try using a Hoover Elite, (fan first) Dirt Devil Featherlite or Oreck XL with a HEPA bag in it, you'll be lucky if you can get the bag 1/3rd full before it's lost 70% of it's power. At that point, the brushroll is just grinding the dirt back into the carpet. The only fan-first uprights I have found you can pack the bag right full is the Kirby & Royal Metal uprights, it seems that fan-first uprights that have the fan positioned in the centre & the dirt tube right in the middle of the nozzle seem to maintain their power better. I would suspect the same could be said of the Eureka F&G uprights & Hoover Convertible, but haven't used either extensively to know for sure. The Eureka F&G's & Hoover Convertible's flaw, however, are those round belts that seem to last a relatively short time & need constant care & replacement.
Brian, do this little test with your Hoover Platinum - With a new bag, turn the vacuum on high speed, put the vacuum on it's back, & put your hand close to the dirt tube on the powerhead, you can feel the airflow rushing into the dirt tube. Then when your bag is 1/3rd to 1/2 full, do that same test, you'll notice the airflow has dropped off considerably. Then, when the bag is full & ready to be changed, go ahead & borrow your Mom's Kenmore canister....with a clean bag in the Kenmore, & after vacuuming with the Hoover with a full bag, run the Kenmore over the same areas. I think you'll be disgusted with what your Hoover has left behind & I wouldn't be surprised if the bag was at least 1/4 full of dirt & carpet fibers your Hoover wasn't picking up.
Rob