The 990 above is mine (and my buddy's Africa twin), both with Model 60, same as model 30 in terms of size.
My mechanic made a couple of aluminum brackets to mount the lights under the cowling, they can be seen in the first pic arising from the fairing's side. It's a bit over engineered and not really necessary but they are very well made.
You can also install them using a simple straight steel angle on each side of front frame, mounted vertical, using the horn mount holes and identical holes on the other side of the front frame.
2007 KTM 990 Adventure
2012 Yamaha BWs 125