In my personal experience combining different opioids like hydrocodone and oxycodone is actually a lot of fun, usually more fun than taking them separately...it's like they have some sort of potentiating effect. 15mg hydro plus 15mg oxy and 200mg codeine I found to be very very fun for about four hours strong, significantly more so I think than if I had just taken 30mg oxy. Others may have different experiences, but I'd say just try and find out! As long as the total dose is one you know you could handle safely with the strongest opioid, you should be safe...but if you go for any high end nodding doses, I'd recommend doing it with a couple friends, just to avoid any potentially bad situations, however unlikely....plus, it's fun as hell to ramble constantly about anything that comes to mind and drive them insane!