Mr. Wishon discussed this topic (and showed test data) in his book The Search for the Perfect Golf Club. If i remember right, the test was done using a 90 MPH driver speed and using driver lengths ranging from 42.5 to 46 (I am probably wrong on the lengths but don't have access to my book at the moment). The distance gain was something like 2.7 yards. However, a miss that is off center can cause a 10 yad loss in distance. As such, longer clubs are harder to control for most golfers. I have a driver swing speed of somewhere between 110 and 115 (112 if I remember exactly... but I haven't had much chance to play the last few years so it is probably lower right now until I get back into "golf shape"). i would love to see the test results with faster swing speeds (no doubt the shorter driver length is beneficial to all golfers because it cuts down on misses. The gains in using a drive rwith extra length are not worth the trade off IMO). Mr. Wishon basically stated that Tour pros are using shorter drivers so we mortals should not even consider using longer drivers.
As far as swingweight issues, I know some use lead tape or tungsten tape (I hate both). Mr. Maltby shows adhesive wheel weights in one o fhis videos (don't like those either). I have only ordered a couple drivers in my 14 years as a golfer (completely inactive almost the last 4 years due to various family health issues and other priorities). . I order them a shorter length (generally 45" ) and state the swingweight I want. Usually, they get it right on (or very close0. Otherwise, I have learned to adjust. The average guy cannot tell teh difference within 2 swingweight points anyhow). Unfortunately, I am both a feel golfer and an analytical golfer
I will be getting my Razr Fit Xtreme in 45.5" (stock length) just in case I ever decide to ditch the shaft (Matrix 7M3 Black tie X-flex). My fitter said the shaft would suit me but I've been a Fubuki guy. I have tried 4 different Aldila shafts and hated all of them. I really wante dto like the VS Proto 'By You' but I spun it way too much (my ball flight resembled a jet taking off.... part way down the fairway. It looked way cool but was not optimal).