i think its solid...5 to 8 spots is normal for a fantasy bench and your good right in the middle with 6 or 7...besides, the more bench spots their are the more it favors savy owners.
I agree with rewarding savvy owners, but no matter how well we draft or use the wire there are injuries involved and luck and we want to make this fun so I wouldn't go higher then 7 and you want to keep the number of rounds even so 7 would work there as well.