Hope you're still checking this.I have two letters I think you'll want to see.
The Dorothy STRONGITHARM Wallin you mention (you missed a "g") is the sister of my gg-grandmother Sarah Strongitharm Casson (b 1810 Otsego Co. NY).They are daughters of Thomas Strongitharm and Mariah Hollis (I don't have any bio for them).
I have ended up with two letters written "home" by Charles ("Chas") and Dorothy Wallin while homesteading in SW Michigan in the 1830's (towns are Berrien and Niles with mention of a St Joseph’s county--which I can't find on the map).One is dated Nov. 1, 1836 (from Niles) and the other simply dated Oct 2 (from Berrien, but no year).
Each is a joint letter, that is to say a 12"x16" sheet in which the couple addressed both sets of parents, as well as the sister, Sarah Strongitharm, in separate notes on the same page.They are in fairly good shape, though each has some small scraps missing around the edges.Both were folded up and sealed, and the address (Thomas Strongitharm, Otsego Co. NY) written on the resulting blank outer side.I'm assuming sister Sarah kept them and handed them down my branch.
I'd be happy to e-mail you a scanned image of these letters, if you're interested.I haven't had a chance to transcribe them, although I intend to soon.
E-mail me and let me know if you're still active on this forum.