Tuxedo Alterations

[Cafe Impecunious]

A couple years ago, I purchased a vintage tuxedo with the label of 'Thorobred Clothes by Bill Kogan / Frankford, Phila.', for $25.  It is a peak lapeled, 4 x 1 double breasted number with extended shoulders and double pleated trousers.  I believe it is from the immediate post-war period, but I can't be sure.  I also suspect that it is a summer-weight number, due to the partial lining and Hong Kong seams.  I also suspect that it was a very nice MTM, if not bespoke, as the cuffs are non-functioning, and there is no loop on the underside of the lapel for a boutonniere.
I would like to alter it to fit me, and would like advice as to the best methods for execution of alterations that are not non-reversable.  The trousers appear to be the easiest to fit, only needing to be brought in at the back, and are to be worn with suspenders.  With the jacket, however, I would like to reduce the padding on the shoulders, as I have a slender frame, and alter to a narrower roped shoulder, as well as bringing in the side and center back seams for a more fitted appearance.
Any advice about the alterations or information on the tuxedo itself would be greatly appreciated.