How long since your last smoke of H and what ROA do you intend for the oxy? Oddly, I have the opposite reaction to oxy (contin I assume). I experience euphoria and all from oxycodone but cant seem to nod off unless I consume massive quantities...like 200mg or so. My opiate goal is pretty much always to get warm and noddy which is one of the biggest reasons I dont list oxyc as one of my opiates of choice.
But to answer your question, of course its ok to mix it up. The issue arises from overdosing due to inexperience or error. If its been half an hour since you last consumed H by smoking it I wouldnt expect the effects to increase at this point. If it were me I would gauge how I felt from the H in terms of oxy (meaning forget you took H...how much oxy would it take to give you the buzz you have right now from the H) and use that as a reference. If by not feeling really noddy you mean you feel "chilled" as you describe 30mg oxy doing for you then pretend you did 30mg of oxy and forget it was H. That DOESNT mean take 30mg oxy now to get the noddy feeling you normally get from 60mg. Id still titrate up in 10mg increments nasally every half hour until you get where your wanting to go. Even smoked the H ime seems to last a hellofa lot longer than the oxy. Id assume you wont feel any less of the H until your lil experiment is over with. Mixing opiate with opiate is one of my favorites to get exactly the ratio of euphoria to nod I like but dont lose respect for the H even if its not gotten you as noddy as you like.
My personal advice would be to forget the oxy for the time being and smoke some more H until you get the appropriate level of nod. Zero chance of miscalculating oxy/H combo negatively that way plus if you want to bump up H a little bit I cant imagine a better way than to do some more H