The Sunday Herald is promoting articles today suggesting it would be an advantage to pro-independence supporters to give their second vote to a pro-independence party other than the SNP.
Wings Over Scotland - a pro-independence but not pro-SNP website - has done some detailed statistical analysis in several articles showing a vote for a second party to be a wasted vote in virtually all cases. The SNP need list votes in order to be certain of commanding an overall majority in the next Holyrood parliament.
If this was the first election in an independent Scotland then I would almost certainly be giving my second vote to a party other than the SNP, but it isn't so I will vote SNP 1 and 2 as I believe that only the SNP can deliver independence. What we do after that is up to us, but let's get there first.
How the Scottish electoral system works:
How list votes for other parties would work out in terms of seats: