I just took a class about blocking a quilt. Get a clean spray bottle and spray the quilt till its really wet with water (soaked not dripping). Using your before washing measurements. Start at a corner and laying it on the carpet begin to stretch and "block" it. You can use a carpenter's square or a laser square to help you get it back to the size wanted. Use the "T" pins 2-3 inches apart and go corner to corner. Be patient in doing this. Once the corners and outside edges are straight and square you can even move in and make sure the seams, etc inside are straight and true using the "T" pins. Then let it dry and set for 2-3 days. This will allow the fabric to remember. This teacher told us that most "award" winning quilts are always blocked to perfection. Give it a try. Hope this helps, let me know if you need more instructions and I'll get up off the couch and get the class notes and send you more details