Boxster S 6-pt harness

[iaincamp]

A few questions: I've installed 996 GT3 seats in my '01 986 Boxster S, which was an easy all-the-holes-line-up swap, and allowed me to plug in the seat belt sensors into the original wiring, though the passenger seat has triggered an airbag warning light. I'm shopping for a Hans-compatible 6-pt harness, and I'll admit to being shocked at the $1040 price tag for a pair of Schroth GT3 Profi II FIAs. I understand that these are a bolt in replacement for the lap belt attachment hardware, but (Question 1) are there lower-cost options that make sense? I assume that I'll need a pair of GT3 Seat Sub Mount Bars ($79/ea), though I've seen others just drill through the floor (yikes!) to install an anchor.
More troubling is Suncoast's warning, " If your 3-point safety belt is not connected, the airbag system may be deactivated. Use with caution, we advise professional installation, and off-road use only."
So...(Question 2) do most track/street users swap in the harness for track days, then replace the 3-pts for normal driving to make sure the airbag is functional? Can both be left in place?
Finally, (Question 3) can I create appropriate mounting points for the shoulder belts on a Brey-Krause roll-bar extension? Should I drill or weld? Thanks!