I can't find anything in the current rule book about pre-travel in SSP. I only see rules like:
8.2.1.3. SSP Permitted Modifications (Inclusive list):
8.2.1.3.7. Internal action work may be used to enhance trigger pull as long as safety is maintained (no visible external modifications allowed).
8.2.1.3.8. Internal reliability work.
8.2.1.4. SSP Excluded Modifications (Non-Inclusive list):
8.2.1.4.1. Externally visible modifications other than those listed in the Permitted Modifications section.
8.1.7. Non-IDPA-Legal Modifications for All Divisions
8.1.7.5. Disconnecting or disabling of any safety device including (but not limited to): manual safeties, grip safeties, firing pin, striker, and hammer blocking safeties, etc.
To me, that means internal trigger work is permitted, as long as modifications are not externally visible and all safeties are in working order.