Roof box fitting

[griswold]

Right i have audi roof bars which i usually fit audi bike racks to or an audi luggage rack
but i have a black(carbon wrap) cheap roof box to fit which used to go on my wifes mondeo but she now has an A6 but havent got bars for it yet, so i am going to use it but cant find any t-bolts to buy i could use the ones off my bike racks for now?
What would be the best way to fit?

 

[OldRedEyes]

my roof box is held on by 4 U bolts

 

[griswold]

Yes thats how it used to be fitted but the audi roof bars are quite high and have thule t slot so need to get some t bolts for it
the old bolts are not long enough so would need to new ones but i would prefer t bolt fittings