解:根据题意,得$AB=(1.2 + c + d) \text{m},$
$AD=(0.8 + a + b) \text{m}.$
∵$a = b,$$c = d,$$c = 2a,$
∴$AB=(1.2 + 4a) \text{m},$$AD=(0.8 + 2a) \text{m}.$
∵$AB$与$AD$的长之比是$16:10,$
∴$(1.2 + 4a):(0.8 + 2a)=16:10,$解得$a = 0.1.$
$ $此时$b = 0.1,$$c = d = 0.2.$
∴上、下、左、右边衬的宽度分别是$0.1 \text{m}、$$0.1 \text{m}、$
$0.2 \text{m}、$$0.2 \text{m}.$