The rack has a threaded boss on the underside of the center tube of the platform, that appears to be there for mounting a light to the rack. However, the mounting bracket included with the light doesn't easily allow for a good angle...unless maybe I bend the bracket a bit, or find another way to do it?

You could bend the bracket. Commonly done in bike shops.
You could also attach the light to one of the threaded bosses on the side of the rack instead.
There are also many aftermarket brackets online.

Bending it is the first thing I thought of...and certainly the simplest. May give that a try if I can't come up with anything else. It would be nice to have the light a bit more underneath the rack if possible, just to avoid any possible conflict with items being carried on the rack.

The wire bracket that comes with the light is intended for the brake pivot bolt and I have yet to see one that actually fit.

The threaded boss in the center line of the rack is probably intended for a fender. The mounts are never quite where you want them.

I made an excellent headlight bracket from a small chain ring. Others have done something similar with a piece of a brake caliper

I wouldn't recommend you mount the light in that location, unless you use a front fender. I've heard of several failures of B&M lights when they got regular spray from below with water.
If you are planning on using a front fender, then I would reverse the mount to get the light as far back as possible, and bend the mount into a C shape make it fit. You can get longer mounts if that one doesn't have enough length.

A common light mount hack is to use an arm from an old centerpull brake to mount the light to one of the side supports. The SOMA wingmann mount is purpose-built but directly inspired by this hack.
Wingmann Light Mount | SOMA Fabrications

I will be using fenders, but they haven't arrived yet. Also this bike won't be seeing a whole lot of wet-weather use...I have another bike specifically set up for that. That said, a C-shaped bracket came to mind, although the one included with the light isn't long enough to bend into that shape.

Peter White has a ton of options, about halfway down this page. The ones for centerpull brakes are already C-shaped.

Ordering from him, however, is an experience. You have to call!

Mounting Lights from Peter White Cycles

I've actually done exactly what you've described, and had to bend the bracket that came with it. I sold that bike awhile bike, but I believe I used some rubber washers on both sides of the bracket to keep it from jiggling loose over time.

You can buy additional brackets too, and get one long enough to have more to bend.

Harris in West Newton MA probably has more brackets in stock, they have a Dealer account with Peter White importing Distributor..


you might put it to the side some, rather than centered over the tire, so the bare wheel spray of wet road grit wont get inside the light housing..

I have mudguards on my bikes.




...

I've attached a stainless steel mending plate (available at home improvement stores) to the front threaded braze-on of the SOMA porteur rack. The headlight is hung from the other end. The headlight is well below the rack, so it's not in the way of cargo or tie-downs, and is protected by the rack from being hit by anything; it's offset from the wheel, and so out of the major water spray from the fender, and it's inside the rack's vertical supports, so it doesn't interfere with hanging panniers. The length of the mending plate isn't too important; you just rotate it back on the braze-on until the headlight is between the wheel and the rack verticals.

The IQ-X is, IIRC, the only B&M headlight that can be rotated in it's supplied bracket, so that the bracket can be inverted while the headlight is right-side up (which is important, because it's not sealed on the bottom).

I'd attach a photo, but I am not yet allowed to do so. :-/