Max height for riser?

I see lots of post about how short you can go with a riser. But how about how tall?
If I have a 6 inch system can I go 5 feet tall for my riser without tweaking the rest of the core?
Dose it increase the amount of heat given off into the room instead of into the mass?
Or dose the whole system just stall out?

I was just wondering cause I'm replacing our old core and realized the manifold is to tall for our new core and the barrel would be like 7 inches above the riser. from what I see 2 inches is ideal. Adding more bricks is easier for me then taking mortared and dried bricks off. I like to know my options before taking a hammer to stuff.

Hey Sam, are you using Clay/sand mortar or refractory?
In my builds, I only use clay mortar.
Refractory is expensive, and you have to chip/grind it off if you want to reuse bricks.
Clay mortar is inexpensive; it pops right off, and you can rehydrate and reuse it!

50-52" are about the tallest risers that I have seen used.
I believe I have read that if it's too tall, it starts losing efficiency.
As far as the top gap between the barrel and riser, I always went with 2.5" to allow for fly ash buildup on the top of the riser.
On the 6" Batchbox stoves, we use 12" as a minimum clearance.
With a J-Tube, a larger top gap would give you a lower barrel temp but a higher mass temp.
You might give 7" a try...

We are using clay slip this go around. But the old stuff is a commercial mix of some kind and it sucks. I think Il bite the bullet and take off a layer of bricks and get that gap a little closer while building up the riser a layer. Worse case scenario itl come apart easier then last time thanks to the clay slip!