Looks like I may have answered my own question. Once I saw from the parts diagram that the headlight lens could be separated from the reflector, I thought I'd take a chance at taking them apart in hopes of nondestructively removing the deflector. And after warming up the seal between the two, I was able to get them apart. A blob of silicon seal covered the lower prong of the deflector where it pierced the reflector, but some careful scraping with a plastic spudger removed enough of it to let me push the prong back through the slot. As soon as it was clear, the deflector dropped right out. A fresh dab of silicon covered the hole, and the assembly is back in the bike ready for another test ride to see if that improved the pattern. I'll update with the results, but the weather might not cooperate for several days.

Scott,
I found this youtube video that asks and answers your very question

https://youtu.be/PZiYA57idMc

Andy
ABC# 15601

It's an awfully wordy video showing how the sub-reflector simply un-clips from the main reflector. Just zoom it right to minute 10 and you won't miss anything important.

What's not explained is the results of doing this removal.

Thanks for posting this, Andy. Would'a come in a little handier yesterday. 😉

Interesting to see that BMW's been using that same headlight and rim since /5 days. I guess you can't improve on perfection, huh?

What he didn't do, and this might explain the water spots he's seeing on the reflector, is to use a little silicon seal to close up the top hole in the reflector where that metal shield prong pierced it. The end of the prong was sealed with silicon seal on my RT, and I did the same before I put the reflector back together.

And I used isopropal alcohol and a soft, lint free microfiber towel to clean both lens and reflector. They came out looking brand new.

And like the video's author, I'm waiting for the weather to improve before I can see if this was a good mod or not.

Just to follow up, removing the deflecter made a HUGE difference in the amount of light available from the headlight. What made an even bigger difference was replacing the bulb with an LED available at ADV Monster. The model I used, an H4 R2, is no longer available, but the Budget H4 LED they have now puts out even more lumens. These two mods have turned out to be very positive improvements in night time riding safety, and I highly recommend them to anyone that rides much at night.

• I tried a three side led headlight from Amazon. The lo beam was better than the original h4 bulb. When I flipped on the bright there was not a noticeable difference over the lo beam. I removed the light defuser and that I  didn't find it made any improvement. 
•  I then read a bid more on the led bulbs and picked 2 up that are 2sided with a small fan attached that runs when the light is lit. 
• This new light setup is both brighter in lo beam and much improved over both previous bulbs. And hi beam is a big improvement. I may try to take out the defuser and see if that helps more. If not I can always put it back in. Lighting has vastly improved over stock without annoying on coming traffic, unless of course I  forget to turn down the hi beam to on coming traffic. I try and stay diligent defusing the hi beam for on coming cars on dark roads.

I do believe the sub-reflector was a hold-over from the 1970's, before H4 lighting was approved by the Federal DOT. H4 was a European standard that had not made it to the States at that time, where we were still running 50W GE sealed beams. The the sub-reflector may have been used to reduce the overall brightness.

Since about year 2000, several high-end car makers started using super-bright, highly focused HID lighting. Maybe that forced the DOT's hand ? These days H4 is everywhere on cars and trucks, and those vehicles are not running the sub-reflector. So by removing the sub-reflector we are now able to get back to what the Europeans had in the 1970's.

It would be interesting to hear from someone with a "European model" Airhead to see if their bike ever had the sub-reflector. 

Scot, do you find the light is still focused? I installed an LED in my /7 and found I lost that sharp cutoff it had. I now worry it will blind oncoming drivers. 

I have a light meter and may try to see the difference in light level. Still not a fan of the blue tint, and I may go back until I can get an LED closer to 4300-5000k.