I'd agree with all that, I don't know how they have suceeded for so long putting out the **** they do. For a time I made MII crossmember kits and patterened mine much differently than Fatmans, proper geometry and things like that. I still have all my patterns and plans just stopped doing them. Lots of cars of all sorts running my crossmembers. Look at Fatmans, one of the things you will notice is the flat top spring towers. The idiots dont even have the sense to put in the proper 10 degree sideways angle for the spring that needs to be there.
I have installed 3 stock MII crossmembers in Chevy's.2 in 39's and one in a 38. I did my 39 about 25 years ago,it still has most of the parts on it from the original installation. I have never paid more than $100. for one complete and out of the car. If I had to pay $500 for a used one today,I think I would go aftermarket as others have suggested.