I have never tested it, nor have I heard from anyone who has tried it.
Against: The 6100, 7100, 8100 and 9150 all share a chipset and most of a ROM, which gives them their characteristics. The 7100 and 8100 do not support 64MB nor 128MB SIMMs because there is a CPLD between the memory controller and the SIMM sockets which appears to steal an address line, and possibly a set of RAS lines in order to provide more memory sockets. Only the 6100, which has just one pair of SIMM sockets supports 64MB and 128MB SIMMs.
For: The 9150 has a FAT AMIC chip instead of the standard AMIC chip found in the other models. It is possible that having the more capable AMIC chip provides more memory addressing capability. However, I don't remember if the AMIC has anything at all to do with memory addressing. I think it has more to do with interrupt handling and I/O control.
If 64MB SIMMs are supported, I would also expect 128MB SIMMs to be supported. 128MB SIMMs are simply a pair of 64MB SIMMs on one SIMM (2 banks). Two bank support exists because 32MB SIMMs are all 2 banks, and if a machine supports 32 MB SIMMs then it supports two banks. So, if the 9150 supports 64MB SIMMs and it supports two banks (32MB SIMMs) then it should support 128MB SIMMs.