I too have no answers but here are a few random thoughts.

Scotland has, throughout its history and from earliest times, been influenced by its military involvement and trade links with other nations. Hence fashions in clothing have been open to these imported ideas.

Dr Alexia Grosjean of the School of History at the University of St Andrews has done work on the Scottish abroad (especially in Sweden). Dmitry Fedsov of the University of Aberdeen has done research on Scottish soldiers abroad (especially in Russia). The National Library of Scotland has a lot of material on “Scots Abroad”. In short, a lot of coming and going that meant that both goods and ideas were imported and exported.

On the Clyde, where I grew up, there were extensive international trading links from at least the mid-16th Century with the Baltic, the Netherlands and France.

The Protestant Reformation also forged extensive cultural links with the emerging protestant nations of continental Europe.

On doublets in particular, it may be worth contacting the Scottish National Museum of Costume, Shambellie House, New Abbey, Dumfriesshire, DG2 8HQ. Phone from Scotland is 0300 123 6789.

You could also Google the Costume Society of Scotland and enquire if any of their members have done research on doublets.

And don’t forget to share your findings with the rabble!