I am not very sure about the various Founders' views on the reasonableness and legality of secession. Early on the Federal government saw the potential negative effects of states leaving the Union and strong measures were either contemplated or threatened in Connecticut, 1814 (Kotromanic #140 above) and South Carolina in 1832. The latter was more denial of Federal authority than secession, but fast forward to 1860, and S.C. was the first state to secede.I would propose that the founding father would have reluctantly conceded that secession was an inherent right
Lincoln faction upheld the proposition that it wasn't ,
Buchanan was the last president of a confederation of states , Lincoln the first president of a centralized Unitarian one
By 1860, the political environment that in the 1780s could conceive of a confederation had changed dramatically. Some may have considered the Constitution a confederation, but others may have had differing political thinking (perhaps one difference of Democrats and Federalists). Whatever the case, by 1860 secession was a cause for open war. Slavery was a justification; it was not the cause.
To Lincoln, and to the North, the future of the United States was as a union, and that was one of the aspects of what seems to me to be the actual American revolution, 1860-65. The Union must be preserved and 618,000 military dead was a price worth paying.
EDIT: (Googled the text of the Constitution.)
The most important statement in regard to the path the US must take was the preamble to the Constitution where "the People" intend "to form a more perfect Union." Therein may be a more definite reply to your post above.