Thanks aragog, I examined my coins from those years and although there is a noticeable difference in the tail on the lower right side of the symbol for Fen on the 1972 coin, the tail on the 1978 looks like the ones from Shenyang, although the left side wheat stalk looks more like those from the Shanghai mint. Interestingly, the tail on the 1972 looks different than the ones from both mints, since it truly seems to be a hybrid between the two designs.
The most interesting thing about this whole subject is that it appears that in most years, the 1 and 5 Fen coins were produced at one mint but not the other, and with the exception of the four proof coins from 1981 to 1984, all of the two Fen coins seem to have only been struck at Shenyang. I definitely appreciate the help, since I enjoy learning as much as I can, even if I don't intend on actually collecting the differing varieties. I am happy enough just to have as complete of a date collection as I can get (I know I can't afford some of the proof only issues, especially in the Great Wall coins and the proof & mint sets from the 1991 to 2000 period).
I already have a complete collection (by date) of all of the 1, 2 and 5 Fen coins that actually circulated, most of which are in uncirculated condition. As I've mentioned earlier, I only have four coins that need upgrading to uncirculated condition (three 1 Fen coins and one 2 Fen coin) if I can afford to do so. On my budget, it may eventually be possible for me to acquire all of the proof and mint set only issues in the Fen denominations at some point, but I doubt very seriously I'll ever be able to afford the 1985 2 Jiao coin or the larger denominations (Jiao and Yuan coins) from the 1986 set, but I will be happy with simply acquiring those that I can actually afford to buy eventually.