HEY!! Lake Mattie, Cool.
Marv, After mentioning Lake Agnes to you in a previous thread i have had a week or two to ponder and have a few more recollections regarding this lake.
Back 3 or possibly more decades ago we had some VERY severe freezes in Florida. Citrus groves Lined US27 from Haines City all the way to Leesburg non stop. Citrus can tolerate some freezing temps but can not take it for very long, and if memory serves correct we had several periods where the temps never got above 32 degrees during the day and was in the 20's at night. This totally destroyed the majority of groves above the I-4 corridor. Now theres nothing but a BUNCH of housing developements where citrus groves used to be.

We had a lot of damage in this area too. Thousands of trees near lake agnes were pushed up and dropped via helicopter into adjacent lakes. (agnes, tennessee, clear and possibly julianna and mattie.)
I remember passing Agnes on i-4 during this period and seeing a huge mountain of pushed up citrus trees right at the edge of the lake.

During the 80's me and a couple buddies would put in at the boat ramp and run to the southwest corner of the lake and drift across. zebco rods and reels, small gold hooks and a couple split shot. Minnows.
picked up several specs each drift. Might be fun to ride this lake a fish finder and see what the structure is