Pilot reported possibly descending below a published corridor altitude in the Grand Canyon SFRA; citing difficulty locating information regarding the flight restrictions in that area as a contributing factor.

Narrative

Was navigating Grand Canyon west bound Supai and tuck up SFRA well south of flight free zone between VPGCF and VPGCA.Turned south to heading 165 approximately 8 miles from VPGCA. Altitude was 10;500 since entering Grand Canyon SFRA.It is possible that I descended below 7;999 altitude associated with the Tuckup prior to reaching southern limit of GC SFRA.Do not believe that I did and track trace shows altitude restrictions complied with however only upon reflection and research I realized it was a possibility. Even though navigating with ForeFlight in some turbulence; I became distracted and am not sure if southbound descent was initiated too early. No other traffic involved.Possible Human error causation. I have navigated GC SFRA many times and am aware of it's intricacies. It is however extremely difficult to find an official place to obtain the insight necessary to fully comprehend where you can do what in an operational description that is not written in total legalize. It is necessary to consult many different sources to obtain the full picture of where what altitudes apply. The chart is ok but should include more descriptive notes on pilot duties within sectors that are outside Flight Free Zones (FFZs). For example; SFRA goes to 18;000 ft MSL. FFZs reach 14;500 ft MSL. One must ASSUME that VFR flight above 14;500 ft and 18;000 ft is allowed but that is not stated on the chart.