Probably for the above reasond, planes like the Bantam have stuck with tractor config, even though pushe rconfig would have looked far nicer....
Nicer is in the eye of the beholder 
Any comment as to safety in either of the configurations
My personal opinion is that the following formula is not in your favour in the event of coming to an abrupt stop from say only 30mph, a 60kg engine then becomes:
F=m.a
a=v2-u2 / 2s
where:
m=60 kg
v=13.33 m/s
u=0 m/s
s=1 m (debatable but I did say abrupt
)then
a=88.89 m/s2
then
F=5333.33 N
then
F=m.a
a=9,81 m/s2 (gravity)
and
m=543 kg
therefore that 60 kg engine is now a 543 kg object heading for my back
