Delysm is Dextromethorphan Polistirex which is a time-release form of DXM. I don't think it lets you get the same peaks / thresholds as 'instant release' dextromethorphan.

Back in my day, all the kids were cold-water extracting their paracetemol/Tylenol out of the combo pain reliever + cough suppressant medications: https://en.wikipedia.org/wiki/Cold_water_extraction

You could probably still do that. Or claim an allergy to the additives in Delsym (a corn allergy is a good one because corn is in everything) and ask to get a pure dextromethorphan formulation from a compounding pharmacy.