Interesting:
With only the “Falcon 4.BMS” theater’s boundaries adjusted in the .xml, even when explicitly selecting the “Falcon BMS” theater in TacView (and also when deliberately selecting the “Falcon 4.0 / Allied Force” theater), the program will display the “wrong” coordinates.
However, when adjusting both the “Falcon 4.BMS” boundaries AND the “Falcon 4” boundaries (I had previously only adjusted the “Falcon 4.BMS” boundaries), regardless of whether “Auto” terrain or either of the “Falcon BMS” and “Falcon 4.0 / Allied Force” theaters are selected, the displayed coordinates are much closer to the actual in-game coordinates. The only problem is that in this case, all default objects, such as the pre-made red KOTAR objects/targets and airports, are now physically at the wrong location (much further west).
Thus, with the following values…
<west>123</west>
<east>134.535600</east>
<south>33.84375</south>
<north>43.04002</north>
…134.535600 being the maximum longitude at the latitude of the impact point calculated using the formulae linked above, I’m getting an impact point of N37°08.12972 E130°20.59026, versus the “correct” one of N37°08.128 E130°20.589. The very small error is probably attributable to rounding.
I strongly suspect that if you get in touch with the BMS developers, they can provide you with the mathematically correct constants and rounding methods (if any) that allow you to code TacView to always display the 100% correct in-game coordinates.