2mm can be quite significant when you have gone to the trouble of custom frame measurements. Even 1/2 a millimetre can be perceptible to some.
Alright, I'll bite. I'm a biomechanics researcher. My brother in law is a continental cyclist and a retul+serotta trained bike fitter who also makes custom steel bikes. we are both mechanical engineers who are starting our own bike-parts business together. we share notes pretty regularly. in our experience the human body is not perceptible enough to tell a 1/2mm difference. simply no way. at 0.5mm you are talking in terms of engineering manufacturing tolerances already (i.e. when your bike parts are manufactured, things are never perfect due to calibration/measurement errors, differences in the machine, etc.) . now 0.5mm would be approaching the low end of engineering tolerances, and I think bike parts are manufactured to slightly better toleracnes than that, but really, I'd bet you it wouldnt be difficult to find bike parts off spec in that region. these tolerances are good enough for aerospace/automotive applications, and they don't even make a difference in my research where I have machines requiring calibration way more precise than any human can need. you can feel the difference of 0.5mm? I sincerely doubt so. I'd bet its in your head. 0.5mm could arise from so many different things ( abit thicker layer of paint, poor lacquer job, improperly done bar tape, etc.) if your fit had to be dialed in to the 0.5mm, you'd spend more time getting your fit right than actually riding.
( in fact, I just did an experiment yesterday. a 4cm long, 3mm thick alumnium plate I tested deforms about 0.4mm when under 49kg of load. Now, I'll grant you that the shape of the sample in question plays a part as well, but it shows you the level of detail you're talking about. I wouldn't be surprised if your bars deformed somewhere in that region when under load, and 50kg isn't an unreasonable load to see your bars under. which would mean that you'd need to take into account ahndlebar flex under load if you wanted to set your bike up right, if according to you you can feel a 0.5mm difference! thats silly !)
now, I'd grant you, if you had some specific physical problem, there IS a chance that 2mm may be important to you. which is why i said I SUSPECTED the OP wouldn't feel the difference. but for the vast majority of the population anything below 5mm difference would be really difficult to judge the difference.
how would looking at the FSA website help me with that? The FSA website just shows the dimensions of the FSA Compact shape how it is today.
Oh, I don't know, how about RTFM - i.e. take a look at FSA's tech support section
where you might find technical reference documents for older products?
^ this. Or you could contact FSA customer support. you do that when you need to get a quotation in your day job, or when you're buying a car, or need help at a store. you ask the staff.
people need to learn to use the search tools.