I've done quite a few like that.
And I've used the brass tubes to run linkages to the side in cases of Tortoises above or below the tracks.
I built my Sherman's Creek bridge -- six spans, four tracks, stone arch -- as a module. Tortoises are below the plywood, which is below the creek bed, and are set back about 8 inches. The throw rods stay parallel to the track level and pass through brass rods to a point vertically above the Tortoise where they meet a vertically oriented throw rod.
I'll post some pics on SNFF.