Long-term follow up: I'm still happy with my modded pedal. Both for street driving and off road. I have not had any issues with the pedal being too sensitive. But I also only do moderate trails; no rock crawling, etc, so YMMV.
Also, the replacement spring has never bound up, caused my pedal to "stick", and it hasn't even made my balls fall off yet!
BTW - I found out that the last number in the spring size (.054) is the diameter of the wire in inches that was used to make the spring. So while it's not directly the spring constant, a larger number here should generally make for a stiffer spring.