The Radbot isnt bad but I am not sure it is overall more noticeable than a PBSF, even though it is brighter. OTOH, the PDW Danger Zone seems both noticeable and brighter than the PBSF with more side visibility. The Vis looks even more so but it is also 5x the cost.

As someone mentioned, there are multi-mode red P60 drop-ins. In fact, there is one at DX (sku 26345). I'm going to buy a single-mode red drop-in for an L2P host and mount it with a Paul Gino on the rear rack mount, but I haven't done it yet. That will put the light a little low, but I think the location will be fine. Without a rack mount, you could use something like a Cronometro NOB. I saw this picture of a rear light mounted with a Minoura Space Grip, and that looks like a good way to do it. Those lights should probably be used with some type of diffuser. I'm not sure what would be best, but for lack of a better idea, I think I'm going to try DX sku 1918.

The W501-B is great. Love mine, got the multi-mode drop in. Here's a thread on it.

http://www.bikeforums.net/showthread...ltrafire-W501B

Contact Tatfiend for the single mode drop-in, maybe you can make a deal. You need it and Solarforce sent him one
by mistake. The Solarforce multi mode dropin is brighter than the DX, so I'll probably experiment with that for now.

Assuming -you really mean day-light operation, then any of the name brand LED blinky head lights would work.

I use flashing lights any way I think I need them. No reason not to point them backward.

Small correction that is a SWING Grip. They are similar but the Space grip has a fixed arm whereas the Swing Grip can be adjusted almost 180 degrees.

The optic you are thinking about will probably require removing the reflector which could dim it a lot; the dome might also interfere with the crown. Mr Bubbles has a great cheapo diffuser in the thread he posted, and another diffuser option is DX sku 52511.

It looks like the lid will be very close to the right size that it may be able to just replace the glass lens. If it is too small it might be able to be affixed to the front somehow or possibly glued to the lens (very ghetto).

Ah, ok.

Here a couple comments I found from people who have used 1918.

"[With a] P60 host... take sku.1918 and remove the white holder. Put a little bit of clear silicone around the edges and mount it to the lens of the flashlight. This gives a wide angle horisontal beam."

"Take one of [sku 1918] and put them in a p60 drop in with the 'bulged' side toward the led. For a lot of DX Drop-Ins it made a perfect press fit. If to big you can sand the edges, if to small you can put a narrow strip of double sided tape around the the edges. Tested both and worked quite nice."

I thought it might be nice to use something that gives a more rectangular or elliptical (horizontal) beam. There would definitely be some light loss with something like that, but the red Cree drop-ins are pretty bright to begin with. I'm only concerned with the visibility at night, BTW.

That could work as a way to affix it and possibly the other diffuser I mentioned as well.

The second idea - bulge down - is backwards and likely not to be too satisfactory. I have an elliptical optic to make the magicshine's throw into a wider beam (see this thread). The optic is similar to that lens but with finer ridges or striations.

Using the 501B, I rested it face up then face down on the lens and did a ceiling test. Face up, it kind of works, but it is so far from the LED it doesnt create the proper pattern - like a focus problem. Face down it is worse - makes a fine horizontal line (like trying to use a telescope for a microscope). With all the light going thru all the optic, it is noticeably dimmer and has artifacts. The soft optic had similar results.

The wider striations in DX1918 may make a big difference even backwards though, who knows...

The stock 501b is definitely too spotty/beamy and needs something; and if it throws some of the light to the sides all the better.

Thanks, everyone, for the advice. I bought the pricey Dinotte 300R. It has the best combination of compactness (no external battery pack), brightness, and mounting ease on different places on the bike for my purposes. I've mounted it on the seatpost below the saddle pack. Other than the price, I'm pleased with the light. The Dinotte customer service and advice was great, too.