Last year I used the J-bar slider on my harness sometimes. This year I started using a Boardriding Maui control system kite bar, which I used with all my kites (BRM, RRD, Naish). Not using a chicken loop, I didn't need the spreader bar hook (on my regular spreader bar, not J-bar), so I cut it off and connected the BRM CS setup directly to the spreader bar. What I found is that the pull from the center lines now comes from a point 2 1/2 inches closer to my body. So, when the kite is directly to my side, the distance from the center of rotation (of my torso) to the point of pull, has reduced from 6 1/2 inches to 4 inches. Since that is effectively a lever, shortening that lever by so much has a profound effect on reducing the torque on my harness when the kite is to the side.
What it feels like is that I can go toeside or walk up the beach with the kite to the side and it's just like when I am using a sliding setup (way reduced twisting feeling). However, I get this benefit without what I felt were disadvantages of whatever sliding system I used....those disadvantages being: the actual moments the sliding occurs when riding, and the fact that most sliding setups put the fully sheeted in bar position even further away from you.
Recently I bought a Ride Engine custom harness with the optional composite laminate spreader bar. I comes with a slider rope to which you can attach a chicken loop. Or to which you can attach a quick release shackle to which you attach a chicken loop or any setup like mine without a chicken loop. The slider worked just fine. But I much preferred the same advantages I had with the BRM setup pulling from way close in. If I tied it in a fixed way to the slider rope it still pulled point from a point 1 1/2 inches further out than I wanted. Still better than a hook, but not ideal. So I modified the Ride Engine spreader bar (copied the idea from a smart friend).
I drilled a hole in the center of the spreader bar and smoothed the edges. I passed a line through the hole and knotted it in back. I put knots out front to attach the BRM CS quick release setup. Even though the speader bar seems real strong, I worried that the stress from the single point of traction in the center would crack the spreader bar. So I added some layers of unidirectional carbon fiber across the face. On the back I layered strips above and below the center hole (so the retaining knot in back is a little recessed and not fully protruding). It is so stiff and seems so strong that I fully expect myself to break in half before the spreader bar gives way. I cut holes in the velcro canvas wrap that holds the spreader bar to the pad for the line to pass through.
I took one picture (shown last) to show how, when pulling from the side, the center pull from the BRM CS is pulling in the same line as the with the slider to the side. And, it feels the same in use to me, without having to deal with the sliding. For me, the whole thing is wildly simple and works great. I imagine it would work with any of the homemade bar setups without chicken loops people are using.
Most of all, if you are not riding unhooked, I recommend trying some sort of setup in which the pull is directly from the spreader bar, rather than from a spreader bar hook.