I've actually dropped over 50lbs over the summer, and the trousers have been the easier part - perhaps because they were mostly made for me in the first place it's been easier to alter them somehow. The RTW ones are all messed up in the rise even after tailoring. Strange how that worked out.
What I think is really difficult is the jackets. They can be taken in, but the length at the front is now all wrong somehow and I don't think they can ever be right completely - either left a bit big overall, or losing proportion. Six inches (at least) or three standard sizes difference, is just beyond alteration territory. I had four suits and two jackets done anyway as a stop-gap, but cloth for eight new suits is on its way and the first new jacket was cut yesterday....got to be done.