You need more than a single name to be certain that they are following traditional naming patterns. Second son after maternal grandfather, eldest daughter after maternal grandmother, second eldest daughter after paternal grandmother. And remember that by this time the tradition was dying out.
We can provide you with families and where they were living up until civil registration in 1855, but the baptisms in the 1800s are not a true representation of the number of children born in Blair Atholl parish. Some were baptised by the Episcopalian church and some parents never got round to it.
William Stewart and Isabel Fraser may have been Peter's parents but you need to track the family and see if their Peter disappears when you ancestor appears.
William Stewart Isobel Fraser Kincraigie Ann 4 Dec 1801
William Stewart Isobel Fraser Kincraigie James 21 Jan 1803
William Stewart Isobel Frazer Kincraigie Donald 22 Nov 1804
William Stewart Isobel Fraser Kincraigie John 16 Dec 1806
William Stewart Isobel Fraser Kincraigie Isobel 20 Sep 1808
William Stewart Isobel Fraser Kincraigie Catharine 15 May 1810
William Stewart Isobel Fraser Kincraigie Peter 22 Sep 1811
William Stewart Isobel Fraser Kincraigie Charles 6 Apr 1813
William Stewart Isobel Fraser Kincraigie William 4 Apr 1815
Another possibility is Peter Stewart and Isobel Ferguson in Middlebridge. They may have had a son Peter.
Basically you need someone to do a bit of digging in the rentals. When did Peter take out the lease on Tomnaguie? Are there any comments from the Factor? If this is the same Peter and mother Isabel at Riemoraig, if so what was the name of Peter's father who would have had the lease?
The Moulin minister made out a census before 1841 of his parish but also included some of Blair Atholl parish. It would be worth finding out if Riemoraig was included.
We would suggest that you get Marigold Massie (Old Oak Genealogy) to use her local expertise to do some digging and get you past this problem, then you can do your own research. Not certain what her rates are, but she can be contacted through the Moulin Family History Group. Here is the link:
http://www.pitlochryandmoulinheritagecentre.co.uk/north-perthshire-family-history-group/news.htmlThroth