I wish to drop by and underline what 'Youngy' here has said. All true and valid points.
Not too many enthusiasts bother to buy supension books, or very actively seek the info in the net. It's all there.
If we take an old rwd Toyota, and wish to lower it like 50mm's. We have to do a lot of labour to get it right. All kindsa pickup points need to be altered. As a rule of thumb - factory original control/trailing arm attitudes have to be restored - period.
I'd suggest maybe only like 20mm lowering with stiffer suspension components. Car may look stupid, but it'll drive great.