This map has a discussion topic which can be visited here

Very large map, 11 res for rines, 17 for aliens, essentially only 2 rooms to hold before the aliens are attacking the marine base.
Marines can rush early and take out 1 hive to slow the aliens down but unless against noobs are unlikely to push further.

Alterations since v1 will make "big room" a greater asset to hold in the game and increase gameplay, aliens have their own door to enter the siege room but if the marines hold the "ledge to defend" they will be able to close an "emergency door" buying them an extra 120 seconds using a weld point.
Changeable room in v1 has been downgraded to "not so changeable room" since the large moving walls were most likely responsible for server crashes.

*If you cannot connect to servers running ns_siegeroomrush_v2 you probably have an old version as i never called any "beta" etc, i just recompiled. To get it working download the zip from filefront and extract the files into your ns directory (overwrite all) or delete the bsp in nsmaps and try connecting to the server again.