Wa Alaikum Assalam Teggy!
Hot potatoe Topic! ain't no one wants to touch this!
I am not an expert, but there is mention of quantities like interest that is double or four times the capital sum is haram...............in the Holy Quran!
But most scholars agree that any sum if it is interest is haram! and it is hard to protect against that ruling.
but keeping away from double and four times is usually easy!