Tell me if this setup is stable.

I tried this setup, but it lacks power. The best result was achieved with the following arrangement: 4 griffins - 1 marksman - marksmen - 1 marksman - angel - pixie - angel.

In the first round, the angels fly towards the griffin stack but don't attack it. The griffin stack moves out of the corner and attacks the marksman stack, killing it (you can take a larger stack, then it won't kill. The marksmen move to the corner, the single marksmen surround the pixies, the upper left griffin stack kills one single marksman, and the pixies move to the corner in full force.

Then the trouble begins - you need the griffins to attack correctly, you need to reduce the marksman stacks, specifically those that will attack now, and finally, you need to ensure that the griffins don't deal too much damage.

In general, out of 3 attempts, it worked once. In a real game, I wouldn't go into the castle with such a scheme, of course.

- the setup is almost the same: 1 griffin - 1 angel - marksmen - 1 griffin, 1 griffin, pixies - 1 angel, only the angels are separated, and we don't use them to attack the griffins, but simply move them down. The griffins attack the pixies, the marksmen move down to the place of the griffins, then the angels go into defense, while the pixies are being destroyed, we shoot down the stacks that move first, but only halfway. Then the angels lazily attack with half-strength stacks (from a defensive position), the marksmen shoot down the distant full stacks, and with a weak Valkyrie, the angels have about 20-30 hit points left if everything goes well. Something like that ;)
In a real game, Valkyrie is usually stronger, and there is something useful like defense or offense, so it is quite possible to take the castle in this variant without losses ;)
P.S. I said that all the marksmen must survive, what single marksmen are you talking about?