Hold on - I don't think the Lee book is a total write off...
Compare it to the Speer book (another one I have) for example... The Speer book starting loads seem HOT when compared to powder manufacturers and, yes, the Lee book. The Speer book, almost UNIVERSALLY, lists starting loads a full grain HIGHER than Lee or the powder manufacturers do. I can't find a single compelling argument for starting that high. Starting loads, in most cases are plenty for target shooting. DISCLAIMER: I'm a relatively new reloader - but I'm fairly well read.
The way I extrapolated my OAL was to measure several different factory rounds using my calipers. Then I went a little bit shorter (maybe .005 to .01" shorter) but didn't approach the MIN OAL that the Lee book provides.
There are several factors one must consider when deciding where to seat the bullet:
a) magazines
b) feed ramps
c) shape of bullet (EX: SWC's have a shoulder - you wouldn't want to seat below that, I wouldn't think)
All OAL data I've seen in any manual or from any manufacture of either powder or bullets also says that it's a recommendation. I would load some small batches at a given powder/bullet combo of varying OAL's (within REASON of course - above the minimums and below max or factory) and see which works for you.
For what it's worth - I've been having great results with the following setup for my .45ACP
Powder: 4.6 gr Win231
Bullet: 230 Grain FMJ RN OR LRN
OAL: 1.269"
At 7 yds with my Springfield XD45 and my dad's Springfield 1911 Loaded I'm shooting 1.5" groups and at 14 yards I'm under 2.5" groups.
Hope this helps.
Andy