Powerflex 755 continuous indexing...

I am using a powerflex 755 to control an indexing conveyor. This conveyor indexes every ~8 seconds. The index length varies from index to index. I am currently using both registration inputs for other duties. Due to the fact that the index lengths are unknown, I MAM to a constant position, then MAH to a homing switch. This method causes unwanted cycle time and since the drive is limited to memory writes, this process wont last forever.
Normally, in a situation like this I would use one of the registration inputs to capture an exact location and then cancel the current MAM and issue a new MAM based on the capture position. But since I don't have any spare registration inputs left, I am looking for an alternative method.
Is there a way to use the homing input as a registration type input?

I know this is an old post, but as a reference I found this KB article which may be relevant for future readers: https://rockwellautomation.custhelp.com/app/answers/detail/a_id/21604 (KB21604)