I realize this is a VERY old thread, but it's the first thread that showed up when searching google for the same question. Not sure when it changed, but as of the 2017 rule book you absolutely can NOT pin your safety. Rule 8.1.8 - Section E from "general rules" makes it pretty clear.
8.1.8 Non-IDPA-Legal Features and Modifications for All Divisions The following features and modifications are not allowed in any division unless otherwise specifically allowed in the rulebook. A. Compensators of any type including hybrid or ported barrels. B. Add-on weights. This includes (but is not limited to) weighted magazines, tungsten guide rods, brass magazine wells, weighted grips, and weighted grip plugs. C. Heavy and/or cone style barrels without a barrel bushing except as allowed in ESP, CCP, BUG and CDP divisions with length restrictions. D. Sights of non-standard configuration (ghost rings, Bo-Mar ribs, etc.). E. Disconnecting or disabling of any safety device including (but not limited to): manual safeties, grip safeties, firing pin, striker, and hammer blocking safeties, 1911 series 80 firing pin safeties, 1911 Swartz safeties. 1911 series 80 frames may be used with series 70 slides or vice versa. Revolver actions may not be modified so that the hammer can fall when the cylinder is open. F. Lights mounted on firearms. G. Rail mounted lasers and bolt-on trigger guard mounted lasers are not allowed.