I'd like to add my $.02 ,the 7-33 is a good machine it like the 7-31 have a larger bobbin than the 7-34 or 7-9 which have the same size bobbin as adler 205& juki 441,we have found that the smaller bobbin gives more consistant thread tension in leather than the large bobbin does,if your sewing thinner materials or canvas & etc then the large bobbin would be better.We have modified the 7-31 & 33 in the past to sew 1" thick of nylon webbing,if you want to sew thick 1/2"-7/8"a 97-10 like Art mentioned is better than any 7class since the single foot it has is much narrower than the wide & clumbsy feet on a 7.
The problem know w/a 97 is getting parts & smaller needles if you want to use thinner thread than 346,since the needle is so long if you where to find any smaller needles they bend & break easy,so you can drop the needlebar down & use a shorter needle like the 794S & will limit your thickness to 1/2"
HTH,
Bob