I have a nice model A 1918 mandolin that has been very good to me for ~ 8 years. The Gibson F2 model is appealing to me. What is the difference in performance? Does it have a better punch in volume? Is it slightly bigger? Is it only style? I would assume the necks to be similar. I do not see many F2 and can not afford F4. what is the difference between the F2 to F4. Thanks!