Good advice Glenn
but don't forget that if you have modified your interior by including a console over the trans tunnel then you might be able to modify a moulded carpet set. You may be able to cut/split the carpet at the top centre of the hump, re-heat and then weight the carpet into position either side of the tunnel and out from under the console. The cut/split section section will be hidden under the console and will allow the carpet to "spread" more easily over the trans hump and onto the floor pan.
I'm not saying that this method will suit everyone's modifications but it might be a solution that people could consider.
Kathi