Nothing under. They are comfortable enough for me. Well - to be honest, I do have Dainese Fulcrum C2 boots that come up mid-calf, and so the lower 1/4 of the pads are on top of my boots.
Normal size pants - none of those "skinny jeans" for me! The leg seems to fit fine as-is. I love the Duluth gear, being a man of "stature" with big thighs and calves, and their jeans/pants just fit fine. Even with the pads underneath!
I have Dainese pants and they work for short legs because the ankle is tight.
They are very expesive but top quality.
Dainese Alien Leather Winter / fall Great pants
Dainese New Drake Air fall / summer
Dainese Drake super Air summer
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My choice at this time (I did have to add an extra snap for when using gym shoes in summer)
Klim Latitude all year rain or shine great pants for all conditions summer / winter / rain or shine
these replace all the Daines above
Stevenolts
I have an inseam of 28 inches and a tall torso that gets me to 5'8". I bump the ceiling in most cars and have to push the seat forward to almost its closest setting....
Back to motorcycle gear.... I shop at Motorcyclegear.Com because they keep the size charts up to date, provide good fitment reviews, and fairly reasonable prices. They also have a fantastic return policy if it does not fit.
I've found myself repeatedly buying Joe Rocket, FirstGear and Tour Master over the years because they stock short leg pants that zip to jackets that also fit over my 38+ inch waist. And I like the fact that the jacket zips to the pants. Having slid down a local road on my back several years ago, I can testify how great this feature really is.