The binaries that are building tonight will allow the astute user to control the operation of the '-final wsinc5' interpolation in detail. The control is done via Unix environment variables, and the documentation is in the output of '3dAllineate -HELP' (notice the all caps, to get the advanced options).
In particular, you can control:
* the radius of the interpolation mask (default=5 voxels, range allowed is 3..21)
* the amount of tapering (default = full width of mask)
* the tapering function (default = 3 cosine minimum sidelobe)
My brief experiments show that setting RADIUS=3 is visually similar to using quintic interpolation, and setting RADIUS=9 or more does not make any visible difference.
Note that the program will get slower and slower as RADIUS increases -- RADIUS=21 is probably both useless and impracticable. The tapering function probably won't make much difference either. Nevertheless, these capabilities are there (or will be there on Friday morning, after the compilations finish) for you to mess around with. Let me know if you achieve anything noteworthy.