I have never experienced any physical discomfort when combining LSD with shrooms, DMT, bufotenin, or mescaline. And bufotenin and mescaline are both known for being quite potent vasoconstrictors.
You can never know these things in advance, but i can't think of any reason why MET would produce more side effects in combination with LSD, than these other substances.
And i don't suppose i am saying something shockingly new here, but it is ofcourse always best to try a substance on it's own first, before combining it with anything else.