As Xexor pointed out, fleece gives the greatest benefit when it is directly next to your skin. If there is any gap between your hammock and the fleece, it will be ineffective.
In order to make my set up completely adaptable, I have my mummy sleeping bag, fleece sleeping bag liner, and sleeping pad. Depending on the weather conditions, I take the appropriate items. For example, if it's going to be in the 20's I plan on taking all three.
Recently, it was forcast to be in the lower 30's so I took all three items. However, it didn't get lower than 40 that night and I had sweat quite a bit the next morning when I awoke.
For wind, I pitch the tarp low and steep. Also, the sleeping pad is key for those conditions and <40