one thing i used to use from a home made device...the pipe insullation foam...for the hot and cold line to and from a water heater and or your main to the house...its the foam like from boggiee boards. its 4ft long and has a slite along the entire length. get some black electric tape and a utlity knife...your set....at 4ft long you can cut it 1in 2in 3in and so on...then slip your sac in the grove and then use the tape to close it up...you just made a foam stretcher ... i went up to 5in but then im a fan of the collars. so no more foam for me.also look into O rings ... lowes and home depot.
...... spelling is off alittle as im way tired.
Thanks!