there is only one way to fin out, first KEEP THE POLYPLOID.. i have only come across one which i didnt clone cause i knew no better and it was a "mutant freak", that mutant freak was the agent orange that gave me 1.4 lbs under a 600w light, id take lives to get her back lol.
id say the odds are descent that with a femd hybridization of the tri and the poly you would find a viable polyploid baring pheno, however as u mentioned the odds of a polyploid are low and more a side effect. so even if u doubled your chnces at one the odds are still very very low imo. but this is my kinda of breeding project so id request that you follow through in the name of science honestly. sight unseen i say u stand a 50/50 chance of getting something viable and a 1 in 1000 chance that one of the viable would display the desired characteristics such as polyploidism or tetraploidism. or even a tetraploid with polyploidal growing shoots lol. 6 plants in two branches? guerilla strain what? haha