That's a pretty nice looking trestle bent, Chris. Nothing to be ashamed of there. If the bents will be the only support for the trestle, they'll need to be quite close together, probably no more than the length of an F unit apart. Timber trestles that tall were pretty shaky and not all that strong. You'll need to add longitudinal stiffeners to each cross brace on the bents as you attach the bents together and to the track deck. You''ll also need to plan for concrete footings for each leg of the bent. You can use seom square styrene stock for this but you'll find you'll need to cut a bunch of them for a trestle that size.
HO Scale Modeler