Micah,
I would not trust this configuration structurally for any length of time. While the .50 inch diameter dimension of the fastener may be adequate from a pure load-bearing standpoint (I'd have to crunch the numbers per Lug Design requirements), the overall configuration is not ideal.
1. You have to rely on turning the bolt in the bore of the stack-up of wing fitting components to secure the bolt - this will wear the bores, over time.
2. Given 1, above, and with the specific structural configuration of the fiberglass sparcaps and associated shear/bearing pads that are buried beneath the .125 plates (wing and centersection spar), it is too easy to impart non-symmetrical loading of the fittings (from flight loads from the wings), such that you begin to impart bending moments in the sparcaps immediately adjacent to the .125 aluminum fitting components. The fit of the fastener in the bore that runs through the entire stack-up of the assembled fittings MUST have a very good fit all the way through - this is the main reason for the per-plans taper pin configuration. When you begin non-symmetrical loading of the fittings (e.g. if the "inside" .125 plate takes the majority of the load), you can start to fail sparcaps in localized bending at g levels considerably lower than what these structural joints are designed for.
Taper pins are roughly 1 inch in diameter at the big end, and generally protrude above the outermost .125 plates between 1/32 inch and 3/32 inch. They are around .75 inch tall, and the taper, per-plans, is 10 degrees included angle. They are counterbored from the large end, to allow installation of an AN960-416 washer and a .250 inch Grade 8 Bolt. Lower taper pins are tapped 14/28. Upper pins have a 1/4 inch hole. The thickness of the bottom end of the pins is roughly 2/10 inch or so. (I'll snag a spare pin and take some more precise measurements, some time this week.). Material is 4130 steel, heat treated to 125 KSI & Cad plated.
