It's not that big, so you might have a chance.I know who I am not challenging to an arm wrastle!!
I have a moveable piece of soft fire brick coated in ITC100 that I move in and out of the outboard end depending on the size of the piece I am heating. It also prevents damage to any burners I am not using. The door side half door also has this on the inside. The new door is just used at idle.Think about making the end caps of your forge out of soft fire brick. Better heat retention on the inside and also configurable for opening size and can allow for long parts to pass through if needed. It also provides insulation and prevents radiant heat from igniting things like your shed door.
Pics? I usually just light the center burner if I have a long piece that needs the end heated.On my forge, I made a shelf to support the bricks and a frame to hold them in place that I can tighten up by using nuts on threaded rod to keep them in place. The bricks do wear at the opening from stuff going in and out but are easily replaced. Another handy feature for the forge is a horizontal rail a few inches in front of the opening. I made one from angle iron and drilled a series of holes in it that I can drop a L shaped piece of stock into. A knife blank or other object can then be held in place during the heat by dropping the L shaped piece over the welded on rod of your blank and through the hole in the angle iron. Or it can just rest on the angle iron.