I know Woodsheal told me alot people wear the 1770's waistcoats under coats,
I have seen some guys who wear Frock Coat's they are alittle long for me.

You could have them shorten up, If I remember right and woodsheal could tell you alot more the Frock Coat 1750's Pattern could be made a Highland Jacket.

You could also go just with the shirt and great kilt,as seen on page one of this thread.