Rod

This would raise oil pressure independant of the filter media, yet allow oil to flow through the filter.

MOST, if not ALL other types of bypass filters have an oriface buily into the filter cannister, or a fitting, to restrict the flow independant of the filter media.

I am referring to the typical "cannister" oil filters on automobiles and tractors from the 40's and 50's.

No I haven't, at least not yet. For the simple reason that I don't think I have an oil pressure problem that needs attention. I'm satisfied with at least 10 psig at idle with warm ambient temp, which I get, provided I use a proper packed filter. The standard relief setting is at 15 psig. You must have seen my other web page on the riser tube. I do suspect that top opening may be a little larger than normal due to the corrosion. I don't know what the original opening size was. Mine's at 1/8" dia now. Perhaps when new it was closer to 3/32". Do you know the original opening sizes, both for the top hole and the cross thru holes? I probably will have to make a replacement for that tube one day and would like to use the proper diameters.

I agree that one could compensate for a lower than normal design filter resistance by making the hole in that tube smaller. You'd have to be careful that you didn't over do it though or you'd reduce the flow and get less than the designed filtering. According to AC, the design is for 1/6 of the total oil flow from the pump to be filtered.

Rod

I wonder if some folks thought they'd get MORE oil pressure by making the hole bigger?

Your 1/8" seems AWEFULL big to me, and MUCH bigger than the restrictors in "cannister" oil filter housings.

The Wisconsins also used the same filter. I wonder what size hole they used? I have a VG4D in storage... I'll check it out one of these days, and report back, FWIW.