It wasn't 'relaxed muscles' that caused the damage but active muscles (the same ones you activate when 'skipping stones') causing the medial rotation of my trail arm stressing the connective tissue at my trail elbow. The result was serious pain (that went away when I changed my swing) and calcium deposits (that have not gone away and may never).
Now I work to get my trail elbow to a position in front of and very near to (if not touching) my trail hip. This requires biceps tension to hold the bend and muscle action of the lats and pecs to get it to the correct position, but I make no muscle effort ala 'skipping stones' to 'throw' towards the target. Eliminating the 'skipping stones' ACTION eliminated the pain but if you looked at my elbow position (when I get it right or on drill swings) it is just as far forward. You can have your trail elbow in the 'skipping stones' (or raquetball) position without the action.
The more difficult thing is getting my trail elbow that far forward in real swings vs drill swings. With my 4.5 drill swing I have my trail elbow exactly where I want it because that is where it is at the top of the drill swing. Once I let my trail elbow get away from this position it's not so easy to get it back there. I noticed in snakedoc's pictures of Blake that he was not happy with one showing a real downswing because his trail elbow was not as far forward as he thought it should be. I can relate. There is a noticeable increase in distance when it is closer to the correct position vs when not which might explain why people report the same or greater distance with the 4.5 drill as with 'real' swings. The limited backswing shown in GtTB fig 16 and the somewhat paradoxical comment (though understandable if you've done it):
Although the muscles are relaxed, ther arms feel 'welded into one piece with the elbows close together.
will certainly help.
It occurs to me that like some who find Blake easier to learn starting with chips, it might be useful to try a Blake equivalent to my 4.5 drill where you start down from a position between GtTB figs 17 & 18 with the trail elbow in the fig 18 position but with the arms and club closer to fig 17.