Is the piece of flexpipe required, or could I just run a 90 degree bend from exhaust up to smoke box?

 

I am running an elbow up to my stack, no flex pipe.

 

no flex here

 

I think the idea of it is to ease installation and to allow the bed to flex some without putting the exhaust in a bind. Mine has it, but thats only because mine came with the kit. Many do not and it works just fine

 

I used a peice of flex on mine because I one haul heavy, and two, I sometimes drive in the hay fields to pull eqiuptment or hay wagons. therefore the frame and bed twist a lot. also, it is very easy for me to replace the flex pipe when it deteriorates over time.