David Kirkham, this topic has been brought up several times before over the last 8 - 9 years. If I remember correctly, you used to be a proponent of the mcleod hydraulic through-out bearings. Glad to see that you come around to my point of view.
Anyways, you mention DOT 3 vs 4 brake fluid. I was under the assumption that DOT 4 was a more "refined,
synthetic" version of DOT 3, and really there wasn't much chemicaly different between the two, other than maybe more "stable" molecules of the same family, kind of like comparing dino vs
synthetic motor
oil. You can mix DOT 4 and DOT 3 I believe with no problem. Unlike DOT 5 which is ?silicon based, and is not compatable.
Maybe DOT 5 would be good to use in the Mcleod through-out bearings. I'll still stick with my external set-up.
For every person changing from external to internal through-out bearing set-up, I bet there are 20 changing from internal to external. Kind of like doctors and Canada. I know of one doctor who moved from the US to Canada (for LOVE) , and about 20 or 30 who have moved from Canada to the US for --- you know the reason.