With the 1/2" bolt and the tubular uppers I use is the same set up we had on our lower end circle track cars. On those bolts for the upper we used grade 8 regular nuts and they never came loose. I have had no problems with the nylocks I use and there are different quality nylocks. One reason I like using the nylocks is that it keeps protects the threads from moisture. On the rest of my suspension I use regular grade 8 nuts with blue locktite. Nut loosening is caused by the joints moving and there is very little joint movement with the uppers and almost none in my suspension. When I opened the holes for the 1/2" I had welded some 14 gauge washers to strengthen the hole area and used a reamer to keep the hole the size I wanted. That being said I have never seen a nylock come completely off the bolt unless the bolt was shorter than it should be. I also do a bolt check on the car before I take it out each year
