ok i have a 35% toc yak 54 running a dle 111v2 smart fly system ATM im running 2 fromco 5200 mah lithum ion packs but looking to change them to same weight but dont want to drop the mah down to far with a full days flight i burn roughly 4000 mah up any ideas of a good battery pack that has enought mah but is around 6.6 oz or less

http://www.fromeco.org/Products/01FRCA123-136/

once agine fromco's are heavy there a123 packs are 11 oz for a 4 cell i will just keep useing what i got untell i  can find a alt battery

So an 8400 mah at 519 grams would be a bit over your limit.  I think that comes out to 18 ounces.  Looks like the Life packs are all pretty heavy when you get the mah up there.

MY bad, I misread the OP, I thought you were looking for a 6.6 volt pack,, not 6.6 oz

If you are trying to drop overall airplane weight I would look to other places besides batteries.

i have droped weight just changed the alloy spar tube for a cf droped it 4 oz then when i rebuilt the dle 111 vs it droped more weight it's cool just wanted to know if anyone had any ideas of a lighter battery

You could post detailed pictures of the airplane inside and out so that we can come up with suggestions on dropping weight without reducing reliability.