I set them up so that my right hand could adjust them, i.e. one strap towards the boom and the other towards the mast.
Clew end. Especially on foil
(usually is more out of the way and less likely to hook the adjustment line, also it tends to be easier to steady with front hand and take rear off with balanced lines and adjust on the fly...but some lines are better for this than others)
I'm using 28-42 and the cleat adj is at clew side and web adj mast side. Both ends attached to boom, LOL
I've always been clew end but thought I'd give boom end a go.
Looks like it's 50/50 so far.
Couldn't remember the video I saw this in last night, but this is onboard an iqfoil course race. Look how often he's tweaking the adjustable harness lines as well as the outhaul. I personally find tweaking the outhaul about 5x easier than the lines while on foil, but they're doing it a lot in races like this.
Side note: The chinook ones with the handle are ones I kept accidentally hooking. The race style lines (like Rytis is using) with an open clam cleat are so easy to change and don't have a hook, but go extremely long so you have to knot them if you need the longest setting to be limited. The severne more rigid ones I tweak a lot less when freeriding. I also recently have tried starboard ones and I like the adjustability but the rope lining isn't quite right and they tend to hang in the wrong place 75% of the time. Will probably replace them with race lines. The point-7 and lisa ones looked great but haven't tried.
I have tried both ways. with the clew end. when you take your clew-end hand off boom to adj, the rig may or mat not sheet out (not scary)...if using the front hand to adj, you have less control over rig while adjusting. and when fully lit on slalom gear in somewhat choppy water.....(scary 
). this becomes more problematic if you got a stubborn harness adjustment clip .
in light winds...not a big deal. my $2 (can't say 2 cents anymore do to inflation 
)
Clew end for me, I just find it feels much safer adjusting my lines with my back hand, especially if going flat out. But there's more than one way to cook a goose.
p.s. Not all adjustable lines are adjustable on the fly.
Select to expand quoteShifu said..
I put mine in the bin.
Did they have unifiber written in them?
always clew hand (back hand) on iq we adjust them all the time and i can't imagine having it on front hand would be so sketchy.
Back hand, my thought process being if I'm holding on with the front hand the sail is more likely to sheet out if I get hit by a gust whereas if I'm holding on with the back hand the sail's more likely to sheet in. I had a quick look at what some of the PWA slalom guys were doing, I think Nico Prien had his adjustment on the back hand and Maciek had it on the front so who knows.
