Bought some cheap generic roof bars off ebay for my 207sw (these ones) with the hope of fitting my 591 to it but being the idiot I am the set I’ve ordered have a slot that’s too narrow for the T track adaptors.
The slot only has 3.5mm of overhang each side, if I used a grinder to make the square bolt heads narrow enough to fit do you think the bars would be strong enough or pull themselves through when I tighten them up??

If it helps I’ve measured the t track bolts at 20mm and the slot on these at about 13mm.

the t-track adapters I’ve seen (on a generic tandem rack) weren’t square, they were oblong. Pretty sure that they were roughly 13*20. Don’t have that rack anymore (long term loan to a mate) so can’t measure / take photos sorry

I have those roof bars. Just get the Thule square bar adapters from Halfords for about £5