If I may, can I give you a tip about non Scots wearing clan tartans in Scotland?

Don't go into a two hour justification lecture, or two minute justification one either. Just say clan X is my family/Clan tartan, whilst looking them straight in the eye. Job done. You have a connection so use it.

Where YOU WILL weaken your credibility in Scotland is if you decide to wear more than one clan tartan. Most Scots are actually far too polite to even ask about your choice and those that might, are probably of the same clan as you, so do a bit, not too much, of clan homework.