I'm not sure how you would rig the lines to your harness independently but if you can figure out a way to that, it should work.
More commonly though, a spreader bar setup is used with a harness and a handle strop. Or you could use a quick release shackle and secure your strop
through that.
If your handles have loops or lines coming out of the back of the top of the handle, you can larks head a 5mm climbing rope of about 18 - 24" in
length between the two lines. If you don't have lines or loops coming out of the back of the top of your handles then you can larkshead your strop to
your power lines near where they come out of the handle. This will require you to create 2 individual loops with ~3mm climbing line so you can
larkshead to your strop and to your power lines.
Typically, I think, you would not attach the harness to the brake lines for anything other than safety. The brake lines will not provide as much
relief, if any, to your forearms because when you let the harness do its thing, if the strop is attached to the bottom of the handles, it is just
going to kill the kite.
Also, the length of the strop must allow you to always be able to reach your handles. So if one is at maximum extension away from you, you still need
to be able to reach it so you can control or kill the kite.
Kite killers are not effective when harnessed in. Safety is always a concern but if you are really concerned about safety and want to use a harness,
you may want to make sure you can kill and control the kite in all circumstances so you aren't overpowered AND attached to the kite.
Harnesses are great. I find they take some getting used to when flying with handles. I tend to fly on the brakes anyway but with a harness and my
kites, I fly a lot more on the brakes with the harness as the brakes naturally want to go forward and become more slack so they need more tending with
the harness.
You may want to go to the flexifoil forum and do a search there on "handle strop" there has been a lot written and several pictures posted to help you
understand how to rig a strop to handles and a harness.
Depower Quiver: 14m Gin Eskimo, 10m Gin Eskimo III, 6m Gin Yeti, 4.5m Gin Yeti (custom bridle and mixer)
Fixed Bridle Quiver: MAC Bego 400, JOJO ET Instinct 2.5 & 5.5, Lil Devil 1.5, Sting 1.2
Rides: Ground Industries