the best way is to buy a bottle of delamination fluid from ebay, £15. were the floor has gone soft mark it out and drill a 7mm - -8mm deep holes with a 8mm drill bit, drill a hole every 2cm in a line to the lenght of soft peice, go up and down 2cm apart once all holes full wipe away any overspill, cover with duck tape and place a empty 5 or 7kg gas bottle on top, leave for 48 hours, take away bottle, no more soft patch, re carpet job done. its a once only mix drill first. it did my van 3ft by 1 foot soft patch now solid...
Richard, February 2011