Corbeau RRS Sportline fitment in '69 Z/28 - need lower slider / bracket setup

[stantaur]

Welcome any ideas on either getting a shop to modify Corbeau's (heavy) double-locking-pin slider/bracket combo for '69 Z/28. I installed the Sportline RRS seat in our Camaro as shown in these pics, but lost roughly 1" of head / helmet room that I'd like to get back by either sectioning the legs of the brackets or trying some other combo you folks have had success with.

VERY happy with how the seats feel and support during early morning twisty road sorties (along with 12.7:1 ratio 35 lb/in valving from Lee's Power Steering + Hotchkis springs, Del-A-Lum bushings, Addco F/R bars). https://youtu.be/bci7vSePwrY?t=12m5s The "match" of the horizontal pleats is close enough, and saves wear from our original 40K mile seats/foam.

Also, I welcome ideas on best seat belt or harness setup to use. The car's only likely to autocross a few times/yr, mostly used for early morning drives in the twisties. The stock belts fit OK with some minor interference on Corbeau's adjuster cover that I may trim away. Could be an easy fix if I can just get an outboard belt instead of the current stock retractor/belt combo.

Thanks in advance for your ideas.