Yes, I'm sure that DMPS does not cross BBB. This chelator has its own pros: DMPS can be taken every 8 hours (6 or 7 is better to surely avoid redistribution) so one can take enought rest; DMPS does not aggravate neuroligical symptoms during initial chelation stages unlike ALA.
DMPS is better tolerated than any other mercury chelator and it is safer than DMSA. /Don't forget that DMPS is designed to BE mercury chelator/
I learnt all this from Yahoo mercury chelation group.
btw Cutler still writes there sometimes.