From the rule book for SSP modifications:
http://idpa.com/Documents/IDPARuleBook2005.pdf
PERMITTED Modifications (Inclusive list):
1. Sights may be changed to another conventional notch and post type (see “sights” in glossary for further information).
2. Grips may be changed to another style or material that is similar to factory configuration (no weighted grips; see “weighted grips” in glossary for further details).
3. A slip-on grip sock and/or skateboard tape may be used.
4. Internal action work may be used to enhance trigger pull as long as safety is maintained (no visible external modifications allowed).
5. Reliability work may be done to enhance feeding and ejection.
6. Internal accuracy may be worked to include replacement of barrel with one of factory configuration and original caliber.
7. Plastic plugs may be used to fill the opening behind the magazine well.
8. Custom finishes may be applied.
NOTE: The slide releases and magazine releases that are standard
on the Glock 34 and 35 models are available as a factory option on
all Glocks available in the USA. Because of this, that type of slide
release and magazine release are legal on all Glocks for SSP.
EXCLUDED Modifications (NON-Inclusive list):
1. Externally visible modifications other than grips or sights.
2. Robar style grip reduction.
3. Add-on magazine well opening.
4. Guide rods made of a material different from the factory part it replaces.
5. Seattle Slug Grip Plug and similar weighted products.
6. A barrel of another caliber that is not offered in the original factory model.
7. Slide lightening (see “slide, lightening” in glossary for further information).
8. Checkering and stippling.
9. Refer to Appendix ONE-A. Firearms-Non-IDPA-Legal Modifications.
Based on this, unless you have direct feedback from IDPA stating otherwise, it would seem that it's a no-go for SSP.