In addition to the great suggestions posted by Overton I think I would up the cull on the LMB by 50 to 100 pounds for a year and see the results, keeping within your 16 inch limit. A 15 acre impoundment is huge. Continue to monitor your population and see if the results are working for your goal of larger LMB. Since you are catching and releasing LMB in the 3-6 pound range I don't think you will have any problems with replacing those taken. I am no expert so take my advice with less weight than others yet to post.
