Look at all this breathing the CPU is doing when it should be handling PHYSICS! Though admittedly GPUs can handle that as well, if you have one spareI still have my Ageia PhysX card somewhere in my storage that I specifically bought for use with Source engine games. I don't have that card in use anymore because of the reason you mentioned above.
"tie the entity to world". What is that? I missed something.That turns the brush entity back into a regular brush, a piece of normal level geometry, if you will, without any special properties applied. If you need to make changes to the visual appearance (size and/or shape) of a brush entity that consist of multiple brushes, you should use the 'ig' button. As Solokiller explained, this disables the grouping of those brushes, so you can modify the shape and size of a brush. When you're done modifying the brush, turn ig off and the grouping of those brushes are restored with all their entity data intact.
Send one man through the portals, sealing them behind him.That's a quick and easy job, sealing only two portals.