Spring measurement on lowered yukon and relocation bracket ?

[Yllwfstbck]

I'm about to lower my 03 yukon. I'm wanting to use bags instead of using coils(mcgaughys 5'' drop coils). Not sure if the measurements are out there but I'm looking for the spring hieght, compressed at ride hieght and total compressed. I'm looking for these measurements to order bags that fit the best. I will be fabing up the mounts and everything. Also, what purpose does the mcgaughy rear end relocation brackets serve. Is it to fix a issue from lowering. What geometry drastically changes when lowering yukon. If I have to make new control arms or that, it's not a issue. I can fab what ever I have to