What kind of moisture levels is the haylage at?  I would expect it should be on the forage analysis.

Also, what soil types are you farming?  If you know soil names, list them; otherwise, are you on limestone? shale hills? creek bottoms? etc.

I raise these questions because of Tim's comment regarding 15 Ton/ac.  That may be a realistic goal, but I am not sure it is achieveable over a large number of acres, and on a long term basis.

1) 6 Ton/ac DM (@ 10% moisture) = 15.4 Ton/ac @ 65% moisture, but only 13.5 Ton/ac @ 60% moisture. So, a small change in moisture levels can make a big change in tons/acre.

2) 6 Ton/ac may be achievable on deep, well-drained soils, but may not be achieveable on some of the shaley hills found in PA. So I think soil type makes a significant difference.

I believe 15 Ton/ac as a goal might be a bit high.  However, I think 8 Ton/ac is definitely too low.  11-12 Ton/ac is more realistic.  You should really be looking at why you are only at 8 Ton/ac.

I am going to say it again....... if you push for a more frequent cutting schedule, I believe you are going to end up with "less" tons/acre.

P.S.  how bad is the deer pressure in your area?  how much is this pest impacting your yields? more than you realize, maybe?