The intake side is ok to use non-modded retainers, good clearances.
The exhaust side should probably use modded retainers for longevity, as the S1X has more exhaust than intake lift. Its likely at high rpm they will just barely kiss the valve seals and over time prematurely wear them out.
I would recommend buying a set of modded retainers and installing them on the exhaust side (less work than re-doing all 12 retainers, since yours are already installed)
Then sell the 6 leftover modded retainers and 6 non-modded retainers as a package for someone else looking to upgrade to an S1X.
Running modded retainers on all 12 won't hurt anything, it just isn't necessary.
Jeramie
