Protected aluminum would be fine as long as you have adequate cooling and don't operate the light in wet conditions.
All these manufacturers produce the same top optical grade reflectors. Optiforms costs more but has the most selection, so they are good to go with if the other companies don't have what you need in stock for just a one off. First check with the others, notably NiPro Optics and Phoenix Electroformed to see if they have the size you need in stock.
Not so easy trying a unique and complex configuration like the long FL with retro-reflector in a Thor host. If you really wanted to give it a shot, you could go with a 2.35" focal length reflector with 9.5" aperture for the primary reflector. Obtaining a retro-reflector and devising a mounting means to the lamp takes much more time and cost than the primary reflector because you'll need a mandrel made for a retro-reflector, and need two precision alignment methods. Your best bet is to go with just a short focal length reflector without retro-reflector, especially for your first go at it. This could potentially produce slightly more candlepower in the beam center but less beam power (less visible beam overall). First thing you need to do is determine the reflector diameter your Thor host can fit, and also the depth. Then you can figure out the largest reflector you can use.
Still, I'm wondering how you would achieve cooling with a Thor host. A 100W can go without cooling under good conditions, but 300W requires forced-air cooling. Maybe forced-air cooling could be done with the Thor host, but I think at some point it may be easier to dump the Thor and make your own housing. That way you're not limited to the limitations of the Thor host in accommodating optimal needs across the board.
It really depends on how much you want to put into this, if it's a fleeting interest or something you want to dedicate your time and resources to. If your objective is to just one up Ra's Maxablaster, it should at least sustain reliable operation in order to actually count as a hand held searchlight. i.e. not over driving the lamp beyond 10% and having forced-air cooling for lamps much beyond 100W.
Gotta say though, aside from being a fun project don't count on it having the merit of rivaling the Maxablaster when getting the research handed to you. The Maxablaster will always be king because Ra created it only with what he learned on his own before any of this information was available. It takes more than a decade to learn everything on your own, or it could be done with the information shared here in the forums by spending probably less than a year to take it in, but the trend lately is to just jump in without taking either of these routes. Repeating here what's already been posted makes the forum redundant and trying to help in that manner is actually helping others to not realize all the fun and appreciation of doing the research to develop a solid understanding and using creativity to spur something new and inventive.
EDIT- By the way, I was very naive and overly optimistic back when I suggested doubling the power to the Osram XBO 500W/RC OFR. That's ridiculously funny.
I dont usually take time off work to reply in candlepowerforums as i usually do so at night before i hit the sack.
But in saying so, you are absolutely correct get-lit.
I may have got a bit heavy handed going into this project wanting to build a powerhouse thrower, BUT never did i think that i was in anyway trying to take the spotlight (get it spotlight lol) off RA. Without guys like yourself and RA sharing their experiences on forums like this great one we are on, people like myself, who love powerful lights (since i was a little kid) but don't have the know how or stepping stone to get into the sport.
I wish i could pay you guys back for all the hard work and effort that goes into these projects, not to mention the passion and enthusiasm and knowledge that was taught to you.
Sometimes i'm afraid to ask for help because i think help usually doesnt come free, but since i've been here, the front page of this website, where it says welcome to the largest and friendliest community on the internet, its definitley living up to that statement.
Yes, i've jumped right into the custom spot light genre, and i feel very privilidged for having the chance to do so, thank God, the internet and guys like yourself for ultimately giving me that chance.
Its a fun past time to jump into definitely, although i have a busy schedule in my day to day life, i still can find some time in taking up this passion and love for high powered torches. Look i dont hang around the LED sections, i'm only in this section as i love the things that are happening in here.
Once again, hats off to you, RA, BVH, the moderators and MA SHA and everyone for being involved and sharing their experiences. Like i said before, i've got life experience in a variety of subjects, i'm a real estate agent in south western sydney, thats my true passion, i work day and night servicing my community and helping them buy/sell/rent property, but i feel like i dont want to just limit myself to the one subject, i need a bit of variety that way, keeps the mind and soul active and fresh.
