If anyone building their own leaner, or contemplating doing so it is essential to understand that there are heim ends and their are heim ends. Going with cheap ones is setting yourself up for a possible disaster. You will find that pricing varies a lot. Look at the rating of the heim ends. Alos , as far a double shear goes it isn't really necesary in th eright application althoiugh, barring any clearanc eissues, will never be a bad idea. In single shear it is not a bad practice to design the retaining bolt to work in conjunction with a washer or some type of enlarged end to assure the heim end ball cannot come out of it's home in case of a mishap or unwanted impact.This is overkill but so what. Heim ends will wear in time and some 'slop' can become evident. Check them for play from time to time. I am not a huge fan of the ones with grease fittings on them but if they are rated you may want to consider them. Also, it is best practice to leave as few exposed threads as possible when installing them. And by all means use a jam nut as you do not wan tth eehreads 'working' back and forth. There are rubber type dust covers avaiable to better protect the ball areas. This may extent life of the unit. It can also retain some slight amount of grease without making a mess. You can find these at speedwaymotors.com among other places. If a choice is available within design parameters between large and small go large! This will give more bearing area and provide longer life over and above obvious strength ratings. I would not be tempted to use tie rod ends for pivots. Some have tried this and it just has too many downsides. Strength may be there but typical manufacturing tolerances are not within what one really needs. Sometimes what seems to be a cost saved does not translate into being the best value for many reasons. Just opinions of course. Safety is always what must come first followed very closely or directly paralleled by function. Looks take a back seat. The best designs, such as Kalich and others, are those that combine all of these things into a clean looking workable system.