Tonka is my home lake and we love it.
40MPH daytime, 20MPH at night.
One caution: At night the primary hot spot, Lord Fletchers, is swarming with Sheriff Boats. If you are loud, you WILL be pulled over.
I have been hassled very little during the day the last couple years. There has been an increase in accidents, so the Sheriff has stepped up patrols. Mostly going after jet skiis, gun-whale riding and, curbing underage drinking at Big Island. It's provided a nice cover for speed and noise.
Let me know if I can offer you any assistance. We'd like to hook-up with you.