I did my class at DiveTech in the Cayman's and had a great instructor. He pushed the limit which now makes things alot easier. Having never dove doubles before it started with dual AL 80's and two 60's as sling tanks (HEAVY!). Was a skills dive at shallow depth. That was the Drill Sgt at half my age... Next couple of dive's AL 80's with dual 40's as sling, 150' depth. Graduation dive was 150' for an hour + about 1 hr 15 mins deco using dual AL 80's and (3) sling 40's, one with travel gas to extend bottom time. 25%, 36%, 80% mix.
Each instructor can do his own thing as long as the base guidelines are covered, which is why I selected TDI. I mentioned prior to getting in the class I was headed to Trimix, hence the added skill level.
Great experience!