Both
co and
main are stressed. CO do MAIN. A bit more stress on CO.
It's the same as the pattern in
It's
MY do MAIN.
It's
JOE'S do MAIN.
It's
HIS do MAIN.
py THAG o
RE an has a little more stress on RE than on THAG, but both of those syllables are stressed.
ubb TOOCE / ahb TOOCE It doesn't matter.
Typically the dictionaries put the more common pronunciation first. Maybe that will help you to choose.
CJ