I get the 30s frequently. I'm afraid I don't know much about dexmethylphenidate potentiation. I know a few tricks for Adderall or other amphetamines- tums or baking soda, NMDA antagonists which seem to drastically slow if not prevent amphetamine tolerance. Those may work for any stims (like ritalin, focalin, methamphetamine etc.) I have no idea actually.
[Found a few suggestions on drugs forum I'll just copy and paste I doubt I'm allowed to link to other drug forum sites: "L-tyrosine, Grapefruit juice, Caffeine Magnesium, Sublingual administration (Placing the pill under the tongue.) Insufflated administration-" which you're already doing. The Caffeine seems like the only viable potential one off the top of my head (which is obvious stimulant+stimulant is a no-brainer for an increased high also increased sweating and heart rate) I'm too tired to research the others]
Lastly I'm afraid the only way to get increased effects is to increase your dose which raises your risk of addiction; you could also try laying off for a few months. Tread carefully if you up your dose and take drug holidays frequently, having any drug in your bloodstream 24/7 is just asking for physical dependance and hellish withdrawals!
Google is your friend try the drugs.com focalin page use the 'for professionals tab' it has all the detailed info you would want. Also look at .gov medical sites you can never go wrong there!
