FranP said..
Hi Taavi, I agree with the proper pumping techique you posted and I do pump in such way.... But this is not the relevant point here.
Regardless of how well a rider pumps, a long&narrow board keeps the speed way better than a short&wide board. The seconds tends to deaccelerate more because it has more drag.
Hmm,
@FranP, at least I don't feel the board noticeably slowing down while extending my arms and preparing for the next pump. Pumping is much more nuanced, it's not just moving your hands, it's more like a whole body thing. Even with quite a bit smaller boards I don't feel that slowing down that you describe. Because while extending your arms you drive the board forward with your legs.
Here's an example with a -10 L board.