Yes, I have your answer.
I'm a 6'-1" fat guy. I replaced my DS seatbelt with.... a PASSENGER side seatbelt.
Turns out that the PS is about 8" longer than the DS. I swapped the PS belt into the DS mechanism, spun the buckle around, and tightened the mechanism 2 full turns to get it to retract all the way. Kinda wish I'd have done 3 full turns.
I had started down this path because my DS belt was VERY frayed. Before the option of the restore places, I tried a 3rd row belt, only to find out it was about 6" SHORTER than the DS. I couldn't reach the glove box while buckled up.
Now, I can pick up something from the PS floor without unbuckling.
Plus, the PS belts are usually much less worn than the DS and they are more plentiful.
Someplace on here is a write up about how to pull the belts. if you need more info, let me know and I'll see what I can find. I know I took pics of it.