Those don't have screws holes for the mounting plate though(???)


Seemed to me that the "mounting plate" (actually a steel strip about 3/4"
wide) had holes or slots to mount on the J-box. The mounting arrangements
for light fixtures are pretty flexible. There are TWO common sizes of
round boxes, for example. If you already have the fixture in hand you can
quickly check whether a J-box screw spacing is OK. If you don't have a
J-box lying about, just take the cover plate off anyout and measure the
screw spacing.