Don't cut the cone get a new one if its too small or too big, your vet will probably let you come with the dog and the cone and change it if it doesn't fit.
Don't cut the cone it could be uneven then and it could be sharp and hurt the dog, just get a new one they aren't expensive.
I don't recomand to put the thing on bananas around the cone to hold it, find some thick band and put it in to hold the cone you can use almost everything.
Has the vet checked out the bite? if not I would go tomorrow to the vet and let him have a look you'll get medications for him and something to clean the wound probably.
Good luck !
__________________ Sun [Owner]  , Fido [Yorkie]  , Mímir [Chinese Crested]  , Kría [Icelandic cat]  , Skuggi [Forrest cat] |