slider help again

[anarchy99]

so finally i will be building a couple sliders, my freind has a whole bunch of trex left over so were gonna use that. so do you sand it down or leave it how it is? also whats the best way to float a slider without it moving a whole bunch. like the pro tour sliders hardly moved when waves hit them. how do you make them do that. also is it better to have it really wide at the bottom or kinda small? and if anybody has any pics of some crazy sliders that are floating please post them so i can use them for examples.