In my humble experiments, I found that creating A-FRAMES in the complex mode yields a stronger bridge support.
This is no surprise, as an 'A' is basically a triangular construction. Look at most metal bridges and you will find that it is made almost entirely of triangles.
Don't forget that Pontifex allows you to create a triangular support in the third dimension as well as the side on view.
(Hint) Use shift and arrow keys to rotate your view.
I agree, however cables (with proper support) can be just as strong and much cheaper, but on the levels where this is not possible, your strategy seems to work the best, in my opinion.
If You build the A's on the Top , you need To hook them with Metal. If you build them down you can hook them with cables:
No: /_\_/_\_/_\
____________
Yes: \ / \ / \ /