Laid on my back and busted my knuckles for 30 minutes switching 3 of the 4 dog springs out last summer.....  trying to push up to compress the spring and get the pin through,,,,now that sucked..   (I've got a Freeman 3 string baler which has 4 dogs on the bottom)  I've helped my neighbor switch his hay dogs and springs on his NH a few times, he can't ever get everything lined up so the stupid pin will go in... :-)