HIS-RN internally threaded insert - Hardware substitution for tight clearance (0.88 channel slot)

Hello Hilti Engineering,
We are resolving a fit-up and installation tolerance issue with a post-installed Halfen strut (HZA 53/34). We intend to use the 1/2" HIS-RN internally threaded insert to secure the channel to the concrete wall.
The issue: The channel throat opening is exactly 0.88" (22.5mm). Standard 1/2" hex bolts and standard heavy-duty washers will not fit through this opening, nor will they sit low enough inside the channel to allow the Halfen T-bolt to slide past.
To solve this, we are proposing to fasten the channel to the HIS-RN insert using a 1/2" ASTM A574 Socket Head Cap Screw paired with a DIN 433 small O.D. washer (0.78" / 20mm O.D.).
We have a required design load of 9 kips per anchor.
My questions are:
Does substituting standard hardware with a high-strength socket head cap screw and a reduced O.D. washer affect the published tension/shear capacities of the HIS-RN system?
Assuming sufficient embedment depth, is this modified hardware stack feasible to achieve the 9 kips capacity, or does Hilti have an alternative recommendation for fastening through a restrictive 0.88" slot?