Not an issue but.

[alexisgayte]

https://github.com/brianmcmichael/dss-vest/blob/f808e8a942305dcc3409f00cf320d06283a761d8/src/DssVest.sol#L56

I would go for math lib instead of the comment.

[brianmcmichael]

We're generally trying to avoid the safemath overhead when we know the numbers are safe. Here there's a require that ensures payment will be lower than amount, so the additional expense is unnecessary.

[alexisgayte]

What happen if "pmt <= amt" check is removed, does your comment make it as safe as it looks? ;)
that was mainly also my point here.