I found out that one way to reduce the chance to loose screws is to leave them in their holes of the lower case right after unscrewing them. In fact, you can put the lower case back in place with all but one screws in place. The only one that I ever needed to put apart was the long one at the top right in the picture (the one that goes close to the display data cable underneath the lower case). Hope this help others! and you stop wondering about shouldered versus not shouldered short (3.5mm) ones :-)
Same here… I could not notice hte difference. Anyone at iFix would like to comment?
This MacBook Pro is the A1278 model!