well, I would suggest you all drawn your own damn things rather than kitbash, then you don't have to think about credits
But like I said, ALWAYS when you kitbash from other drawings, you need to credit. If it starts to make too long credit list, i refer back to my 1st sentence
Only when you kitbash stuff from equipment sheets (or equalent stuff) or kitbash from your own drawings, you don't need to credit.