Palmer was fine but I wouldn't want to experiment with Tierney at CB in a back four, so he comes in at right-back.
Not sure about Caulker but also not sure about any of the other CB options. They're all much of a muchness, so it might seem a bit strange to try another new pairing at this stage - but I don't really want Mulgrew involved and at least Caulker has that big match experience. Albeit not at international level.
Armstrong just gets the edge over McGregor for me, but if he's still not playing at Southampton by the time these matches come around then I'd maybe make that swap.
Also not much between Christie and Forrest, just think he offers something a little different.
Keeping the faith with Shankland.
Marshall
Tierney - Caulker - Findlay - Robertson
McGinn - McTominay - Armstrong
Fraser - Shankland - Christie
McLaughlin, MacGilivray, Palmer, Taylor, McKenna, Jack, Fleck, McGregor, Forrest, Russell, Burke, McBurnie.