Nick,
these are tough drawings to work with. Is it possible that the upper drawing is showing the limits of the flats on the top of the wood members where it says 52 inches less 1/2 inch? and that this dimension has nothing to do with the hole locations which are NOT shown on the strap, either?
A symptom that this might be correct is that none of the other hole locations are shown - just wood dimensions. the hole locations must be indicated on the bracket drawing. All of them.
When the drawing says to drill the hole in position as it does on the aluminum drawing, wouldn't you assume that means with the wood parts in place? of course then, you can't see the aluminum where you put your prick marks for drilling. Or maybe this is like Joe's Baby, where the hole gets drilled on the plane with brackets in place?
Generally, it is good practice in manual (non-CAD) drawings to try to show a dimension only once. this not only reduces confusion. but avoids possibility of exposing an error - such as the one Jeff showed on his thread where there were two dimensions for a hole location, i think on the throttle quadrant, and clearly only one could be right - but which one??
I liked the 1 25/64 +.010/-.000 on the control drawing. I know what the intention is but are you going to be able to work to those tolerances when you weld this up?
keep at it. I'm delighted that you are sharing so much with us.
best, John