It is indeed achievable. Spoiler about the solution follows…

So you decided to go on? Okay then.

If the first card is Jack of Spades, South trumps, then discards to be trumped by North, and the rest is trivial.

If the first card is a heart, South trumps, then discards to be trumped with North’s Ace/King of Spades. North then leads with the other to get the Jack out, and the rest is again trivial.

If the first card is a minor, North trumps with Ace/King, then leads a small spade to South’s Queen, which also gets the Jack out. Another minor discard to North, and the rest is trivial.

This requires a minimum of only 16 HCP for grand slam (SAYC suggests 37). Is there an arrangement with lower HCP which scores a with-trump grand slam?