Check out Mark D.'s post at The New Reform Club on how many of the "non-key" (as in not 1st tier) Founding Fathers get short shrift by scholarly authorities. His post on Deism is good too.
It brings to mind a criticism that the more heterodox Founders get undue attention. And it's true the 2nd tier folks seem more identifiably orthodox than the "key" Founders.
Still, given virtually all of the Founders, both orthodox and heterodox, were associated with churches that had orthodox creeds (which they may or may not have believed in) it's a mistake to fall into the trap of thinking "except for this, they were all that." As in "except for Jefferson and Franklin, they were all Christians." Or "except for a few deists and unitarians, they were all orthodox."
If we want to know more beyond the above noted formal and/or nominal affiliation with churches with orthodox creeds, then an investigation must be done according to a method that looks for every available piece of evidence, finding hopefully smoking guns that are often hard to find. Both sides are subject to this exacting method of scrutiny. Both sides equally share the burden.
There were also hundreds (or more) of Founding Fathers, depending on how we measure. All of the signers of the Declaration and members of the Constitutional Conventional who voted for the Constitution (or perhaps members present but didn't vote for the Constitution, but like some Anti-Federalists, who were against the Constitution, but supported the Bill of Rights). The original federal politicians too.
The name that comes to mind is Aedanus Burke. In James H. Hutson's The Founders and Religion a Book of Quotations it dates his life (1743-1802) and says he was a "South Carolina solider and judge; member of the First Federal Congress, 1789-91."
So this Burke was perhaps not a first or second tier Founder, but one of the many third tier ones. This is what Benjamin Rush said of him:
I have long observed that men may be Deists, and yet be warmly attached to the forms of the Sects in which they have been educated. . . . Mr. Hurt informed me that Judge Burke had assured him that he was made a Roman Catholic and a Deist nearly at the same time by two different priests in one of the colleges in France.
This one quote doesn't "settle" the matter on Judge Burke. Rather it's probative. He had a Roman Catholic background but second hand testimonials of professions of "Deism." And we don't even know what kind of "Deism" this might refer to.-- Benjamin Rush, ʺCommonplace Book,ʺ July 1792. Corner,Autobiography of Rush, 223–24.