I would second the Toplight Line plus. It is as bright as generator taillights get, and the big honking reflector makes it as bright as it needs to be with traffic coming. The only reason I wouldn't consider it is if it was a 'problem' fit (no place on the seatpost, saddle rails, or rack), which doesn't seem to be the case for you. FYI, Topeak sells adaptors that switch the 20mm vertical reflector mounting to 80mm rack mounting...limiting where you can put a Toplight only where your imagination stops you. I have mounted one on a rack, a seatpost, saddle rails, and even on the inside of an hourglass braze-on on a seatstay.

I've got a Secula as well (mounted on a fender)--i find it less conspicuous than the Toplight (both in a good aesthetic sense, and a bad, 'not as obvious' sense).