Suel Archanamach and Spellsword

[Jugonshi]

Do Ignore Spell Failure from Suel Archanamach and Spellsword stack?

For example, somthing/Suel Archanamach 10/Spellsword 10 has Ignore Spell Failure 15% from Suel Archanamach and 40% from Spellsword. How much is the total amount of this PC's spell failure reduction? 15+40=55%? or 40%?

[Calirion]

I think "ignore spell failure" is typically attached to a specific class, so that the percentages don't stack. The character gets the 40 with the spellsword and the 15 with the suel archanamach.

[Jugonshi]

I was expecting them to stack as Spellsword is not an independent caster class but +1 to existing class type.

But you are right. I have tried the build on a mod and those two abilities did not stack.

[Calirion]

Oh, I forgot they were part of the same spell progression. In that case they still won't stack, but the character should get 40% consistently.