i know its been a month since this was created, but after Quba referenced me i thought i might add my 2 cents here too
what helped me with the ramps:
take care that the angle between each segment isnt too high, to avoid bumping the corners
so: make more segments for the same ramp, to smooth it out if you have to
second: when the ramp feels awkward make it steeper and see if it is better afterwards - remember, the steeper the ramp, the less chance you have of randomly bumping into an edge thats not *steep enough* and makes you just stand there
if you look at the last ramp of my c course you can see how steep it is - it can still be surfed, and as far as i remember i never stucked on it - if and when i got stuck it mostly was the second ramp, somewhere in the middle... sometimes on the first if i take it too high and in the wrong angle - might have to add more segments there, but too lazy to fix that, havent seen too many people bump anyways...
also: i havent tried making clean ramps yet, i have no idea if this works for *cleaned up* ramps too, though i imagine source might get confused on clean edges, and the ramps might get bumpier after cleanup, because of the limitations source has vertex-align-wise (cant get below 1 hammer unit, without your edges messing up majorly... also try making a straight ramp and put a clip right beside it, but not into it, so the edges align, youll be able to stand and walk on top of the ramp because 1 unit edges are enough for players to walk on ... so that too could create problems along the seams)
so: make the ramps overlap in both directions to make sure those problems dont occur...
i can send you a vmf of the ramps if you still want/need it
and lastly, is this your video? because us germans are not allowed to watch videos with copyrighted media in it -.-
oh, one more thing:
if im too late and you already found the sollution to all out potential surf-ramp-creation problems
mind letting us in?
laters
oh, ps and stuff, while im at it:
surfing on a curved ramp for 10 minutes without bumping is not possible i think - because of the source engines way to handle things - there is just too much that can go wrong, i mean, you can even occasionally get stuck on vertical walls that are perfectly alligned as long as they are horizontally divided into segments, and you can STAND on vertical walls that are angled if you do it right - i really dont think there is a way to perfect this...
mb you can make the ramps surface *slippery* to get it a bit smoother, like making the ramps of an ice material or something... havent looked into that up to now, but that might help...