Sharing is the way to go forward - none of those tips were originally my own.
I can merely read and have a decent memory (for my age).

AFAIK - the need for high alumina content of the "26" bricks (as to compared with lower temp grades),
are that the content forms a greyish Al2O3 protective oxide cover on the A-1 wire when glowing,
thus prolonging the life span of the wire.
This is particularly true when running the oven/ kiln up to and above 1300C,
where the wire really begins to suffer, and where the sodium silicate would become more detrimental.

Water glass is usually one of my go-to materials (as a cement binder, water & fire protection, glue etc),
and it would've darned useful for (cheaply) reinforcing these "26" series fire bricks...

When my own melting foundry/ heat treatment facility (4 kW, 400 VAC 2-phase) eventually will be built,
I guess I'll have to live with the bricks' brittleness w/o any Na-silicate mortar,
having a thin stainless plate as a protective bottom?

Without intention of hi-jacking your thread:
I haven't actually found any suggested mortar for Kanthal A-1 & "26"-grade bricks anywhere...
-Any other readers here that have done so - please pitch in!

Cheers
Johan