I was in a similar boat as you with the rear brake line. When I did all my suspension I did the front brake lines only. I went through 3 different sets of Streamlines and not a single set were the same nor did they fit properly. I ended up getting Galfer lines up front and have been very happy with them.
After blowing out my rear brake line I went with a Galfer rear brake line, the fit was spot on and the feel is great. After finally getting the rear brakes bled, a royal pain I might add without a vacuum bleeder, the pedal feel is nice and firm but certainly not overkill. I guess the best way to describe it is that it's a much more confident feel in the rear brake. I haven't noticed any tendency for easy lock-up or a touchy feeling to it. I will say this, it was a little adjustment after being use to the stock line and the squishy feel of it. It should be noted, some of my squishy feel could have been due to the brake line just being crappy and on the verge of blowing out, which it eventually did.
When I did my rear brake line I rebuilt the caliper and went through the master cylinder as well. Starting with a basically dry system and everything connected I filled the resi and pumped it a number of times slowly, keeping an eye on the level in the resi. I did this just to get some fluid back into the components of the master cylinder. After that I hooked up the vacuum bleeder and bled my brakes like normal. I found out it is VITAL to keep an eye on the resi, I sucked some air in and I essentially had to start over at the resi, my dumb mistake there! Once I got the rear brake bled properly and no air at the caliper I just did a bedding in on the rear brake pads and have been really happy with the brakes since.
That's what I went through and what I've noticed with my set-up. I'm in no means at the level of riding skill as you are so you may or may not like it. Wanted to provide my opinion and the things I noticed though when I did mine. Hope it helps Duster.
11' KFX450R, Stg 2 HotCams, JE Pro Series 12.8:1 piston, Pro Bounce nerfs, Accel coil, CV4 hoses, Engine Ice, Dasa exhaust, FCI, Wiseco Fuel Programmer, Hiper beadlocks, +1 stem and anit-vibe clamp, Lonestar long travel arms, Fox float evols in front Fox podium 2.0 rear, Trailtech Vapor, PRM skid plates, Rekluse Core EXP 3.0, All Motor Graphics kit, Precision Elite stabilizer, Quadtech hump seat.