I would consider the suction tube to be "on the side" for both SP and Non SP models. It may be slightly more to one side on the SP WT, but I think any difference in performance is negligible. I actually pulled out my SP WT yesterday to vacuum our upstairs carpet. Those really are great cleaners; I saw one on eBay that was NIB, so if that's the model you got, contragulations! You should only need to replace the flat belt (belt number 38528-035), and I imagine you'll be good to go.
One big mistake that users always made with those machines is they would run it on a thick carpet with the height adjustment set too low. That causes extra drag on the brushroll, and the V-Belt then starts slipping. The groove in which the V-belt rides on the agitator can start to melt, and eventually they stop gripping one another. The only fix for that is a new V-Belt and a new brushroll. I can't even begin to tell you how many V-Belts and brushrolls we replaced at Hoover. They should have somehow modified that design to prevent that slippage from happening.
Also, don't move the height adjuster knob or the brushroll on/off knob unless the cleaner is in the upright position. You should lean the cleaner forward, or lift up on the front of the nozzle when you move those switches. Again, another odd design quirk that users would ignore, and then the knobs would break off.