I am not sure what emergency you are trying to protect against with an accumulator..

Most of the time I have read of them they are used on racing engines doing 6000 rpm plus... in case of an oil line blowing out.. and include an ignition shutoff ,,, and this accumulated oil is an attemp to keep the bearings lubed while the engine gets shut down....

From an engineering viewpoint... with this limited amount of oil, and relatively slow injection ... I think you will want to examine the relative friction looking from the oil pressure sending unit hole... it may very well be that the oil will wind up traveling toward the oil pump instead of towards the bearings...

If you are worried about an engine run on after an oil line blowing it might be more effective to install a vacuum switch which would activate the regular shut off on the engine based on a drop in oil pressure... like some cars have for shutting off the electric gas pump in case of accident ...