just jumping into clear a few myth.

1. Poser is Large Address Aware already (since P8 at least).

2. any 32-bit programs, will take max 2Gb user-ram (+2Gb system ram) in a 32-bit Windows environment. Unless the program is LAA, and unless that Windows environment is set to alter that into 3Gb/1Gb. I wrote a tutorial about that.
   Note: for 32-bit Mac OS, that 3Gb+1Gb is set automagically for LAA programs, no extra OS fiddling is required.

3. any LAA 32-bit program in a 64-bit Mac / Windows environment gets 4Gb user ram, as stated in http://msdn.microsoft.com/en-us/library/windows/desktop/aa366778(v=vs.85).aspx (thanks, Wimvdb). This is what OP is experiencing: just Poser in Win64.
   4GByte is the limit for all 32bitters, as 2^32 -1 = 4.294.967.295 bytes addressable.

 = = =

4. I've tested bucked-effects recently. Smaller buckers require more overhead, larger buckets require more 'thread-memory' and become less efficient in smaller images with rendering 'hot spots' (small areas which require lost of time).

The result: size 32 is optimal, in memory and time, except for really large images (4 megapixel and up) in which case size 64 becomes slightly better. All values below 32 do take (far) more time without requiring really less memory, sizes above 64 are ramping up in memory use but don't deliver faster in the end due to the inefficiencies mentioned.

Note by the way that you can set a MAX bucket size only. Poser can chop that at will, internally. Fixed bucket sizes were P4, if I recall correctly. Might be P5.

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Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though