Weight may have a little to do with glide but I only notice it solo compared to tandem or loaded vs empty.

Balance would be obvious and just moving something lashed in makes a big difference. Equal front to back is ideal. Stern heavy is more work and bow heavy is torture.

Were the pads much different than what you're use to? This might better simulate a niece's butt:
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There's another design out there too but I can't remember the name of it at the moment. It's not two pads, more of a wraparound deal. Anybody know what I mean?