I just completed the TecDeep course with Monty. That was my first "vacation" in six years. It was an an excellent course with some pretty special dives. If you decide to take it, read the book and answer all the questions before starting the class. That will make your life way easier.
About two years ago, I switched to a back-plate and harness. With no pockets you end up having to clip everything to D-rings. That includes a dive knife and a dive light. The goal was to obtain a compact powerful light with batteries that can be purchased here in Roatan. Some flash lights require CR-series batteries. As of yet, they are not sold here. At times, you can't get AAAs. Another point is not wanting to carry around a canister light. Nothing against them, but why carry one when teaching Open Water?
There are numerous options for lights and I have worked my way through a couple in attempts to find the one. They include Intova, Mares, Underwater Kinetics and the latest, a Hollis Mini Led. Not sure this is the one yet, but so far it is an excellent choice. It uses three AA batteries which works well will with Energizer rechargeable kind. To use it, simply turn the handle and there goes your highly concentrated beam of white light. Keep turning and the light turns off and you will end up flooding it. It is compact, about two inches in diameter and just shy of six inches in length. You can purchase this light at LeisurePro for $99.00.
There is one issue I have been having with the light. At 100 feet, turning the light on has been impossible. At about 70 ft it is easier but there is resistance. It seems to be the air compressing. I plan on switching back to regular batteries just to rule that out.