Suggest Dosage For Methylphenidate While Treating ADHD

Question: i'm in good health and have been treated for ADHD for appox. the last 2 years with stimulants. my insurance will only pay for generic meds. i don't have a alcohol or drug problem and have never been in treatment for either. my problem is i build up a tolerance fairly quickly to the meds and they don't last for as many hours each day when i take them as reported by drug co's. usually a IR tablet last 3 hrs. and a ER capsule lasts 5-6 hrs when working well. i have taken amphetamine/dextroamphetamine, dextroamphetamine, lisdexamfetamine & methylphenidate. i was last taking methylphenidate (5/10 scale) and was starting to build up a tolerance and a week ago i switched back to dextroamphetamine after not taking it for 6 months but it is not working at all (1/10). i have never taken focalin, desoxyn or Evekeo(amphetamine systemic). question: i already have some tolerance build up to methylphenidate (20mg.-3 times/day) should i try dexmethylphenidate, desoxyn or go back and try Adderall again? it has been about 12-14 months since i last took Adderall.

1. i will ask my provider about increasing my Methylphenidate IR from 60/mg/day up to 80mg/day.
2. generally, if i have built up a tolerance to the Methylphenidate IR, would i already have a tolerance to dexmethylphenidate IR that I've never taken before?
3. next time i make a medication change, please list in order (#1 to #4) that you would recommend i try from these 3 new medications. (focalin, desoxyn, Evekeo) that I've never taken and adderall that i haven't taken in the last 12-14 months.
5. are there any other stimulant medications, generic or non-generic we should also consider along with the 4 mentioned above when a med change id needed?
thank you...