We have some dedicated heavy duty (6 ton I think) jack stands that we added 1/4" wall tubing instead of the adjustable part. This is welded permanently to the base. They are about 40" tall and have a piece of channel to bracket the frames.
These are used for building our trailer frames and not for supporting cars or trucks.
We also use the double support method when using jack stands. Some of the trailers we get in for repair are barely able to support them selves. Some are wired together, some are just falling apart, some are already worse. needless to say not a real joy to work on. I like to say we charge once for the repair and once for endangering everyone on the road.
I always put something else besides a jack stand under vehicles too. I had a 4 ton stand shatter the top end as I lowered the jack on the front of my one ton dually. Scared the living death out of me. Luckily the jack caught the truck and I was not under it although I had already put an extra wood block a ways back on the frame. It only dropped a couple inches before it hit the jack and there was only another inch before it would have hit the support but it still made me stop and re-think the jack stand situation.
I don't trust them, especially since the great majority are made out country.
You simple can't be too safe when crawling under vehicles or anything heavier than you are.