ceramic fiber board questions

Planning on a new build this summer. Kicking around ideas... I have all the firebrick I could need BUT...   been thinking about incorporating some ceramic fiber board  into at least the burn tunnel and start of the riser.  Seems 1" is the thickness that most are using. I read somewhere that Matt Walker liked the 1" but a person could use the 2" if they could afford it. I'm wondering about the 2300 F 1/2" board ? Is 1/2" enough to keep the heat away from my backer bricks ? Its quite a bit cheaper and seems to have 3 levels of durability,  regular , moderate strength and ultra strength. Of course the harder ones are much more than the regular, all seem to be 2300 F A few of the 1" are offered in 2600 F .  
If I use a ceramic fiber board do I need fire  brick as a backer or is a red clay brick sufficient.
If I were to splurge on enough board for a riser, would 1" work ?  How does a person (join/seal) boards on edge to make a tall enough riser ?  Is wrapping a riser with rock wool necessary if its built with ceramic fiber?

Got a reply over at donkeys, thought I would share it here.  1/2" is considered to fragile to use. 1" is acceptable  at any location but 2" would be preferable in the floor and roof of the burn tunnel.  
EDIT)   Using 1" ceramic fiber board, firebricks are not needed  red clay bricks are perfectly safe to use as a backer .

No more perlite clay risers for me.  I have been shown the 5 minute riser!  Created by (pinhead) 1"ceramic fiber blanket inside a stove pipe ! That's it !  What a great idea ! And it can be lifted off in case of a rebuild ! Think how much more room inside the 55 gallon barrel without a 16 gal barrel inside ! No need to buy ceramic fiber boards for a riser , and the blanket is cheaper ! Win Win Win. Thank you Pinhead !