I was just going to post the same thing.
Replacing the pulleys on the lead screws was the first mod I did to my FT-5, during the initial assembly. I used 40T pulleys for a 2:1 ratio. The original 188mm belts were then not large enough, so I swapped them for 200mm belts which are the perfect length.
I don't print any tall vases, so the reduced speed of the Z-travel has never been an issue. When I convert to a single Z-stepper, I'm fully planning on keeping the larger pulleys on the leadscrews, as I believe it will be especially beneficial in that situation.
Don't forget to alter your steps-per-mm values in the Marlin config file after the change, and then do a calibration to fine-tune it. Rather than printing a calibration cube, I held up a precision ruler and moved the Z-axis "200mm", and used the difference between the actual travel and intended travel to figure out the correction factor for the Marlin config. That should be a lot more accurate than a printed calibration cube, as the calibration cube makes some assumptions on your first layer height that may or may not be correct, and using 200mm rather than 20mm reduces the impact of the precision of your measuring. It's one time where the ability to step the bed height up/down by 0.1mm comes in handy.