In the good ol' days, the general rule of thumb is 1* of timing per 1000'. So, if the PCM is programmed for 15* at sea level, then at 7000', it would need to be adjusted 7*, making the max timing for you car 22*. With your mods, your adjusted target range, acoording to Rogue'* post would be around 25-27. That may seem high for most of us, but then again, most of us are no where near 7000'.
At the same time, your fuel/air tables are alot different that what we're used to as well, and that was very likely programmed into your PCM, so that the ratio along with 22* of timing work like stock. Way up there, you're engine is getting a lot less oxygen than ours is, thus will tend to run richer if the ratio table isn't changed.
It should work the same as our stock does with leaner ratio and 15* max timing, at 1000' or less.
Granted, the range of timing that is programmed into our cars will probably work ok up to about 3000', maybe a bit more. Then, ones are likely losing performance if the chip still reads 15* of timing.
Here'* an exellent article I found that really puts it all into layman'* terms:
Anyone, feel free to correct my thinking here if I'm off a bit.