Double Difficult. Lumix M4/3 14mm

I am doing practice samples of the joinery used for the dividers between panels of the blanket chest I am making.  This is tricky: both mitres of the molding, and the square shoulder have to come together simultaneously.  There's a sequence of cuts using a jig, but the final fit requires shaving the miters with a razor sharp chisel until they allow the shoulder to drop into its socket and just kiss the quirk of the molding.  This is the joinery which the old tradesmen used for the mullions of window frames, and the doors of display cases back when there was real skill aplenty from a lifetime of doing it every day for years.
There are eight such joints on the blanket chest; all must be perfect.  My Editor says, Can't you just make things easier on yourself with a simpler design?  It's the journey...