I designed a "homemade" approach to my grass strip a few years back and flew it many times in VFR conditions, it was loaded on the panel mounted Garmin 496 with an external antenna so was pretty much rock solid. I kept refining then flying it always in VFR conditions over and over again till I had it nailed. Then the first day I went to try it in actual I was lined up 15 miles out on final at 4500 ft with the overcast between 1000 msl (750 AGL) topping out at 3000 and I started my descent for the soup. Just before entering i thought to myself f
K this! powered up, turned south and headed 15 miles out to sea, picked up the Leuchars ILS and rode it down to VFR then flew back to my strip low level with plenty of head height/ground clearance from the ceiling.
Bottom line, it just ain't worth it.
Edit to add, I had the GPS with the signal and accuracy alarms set which would pipe an audible warning thru the audio panel to my headset. Still didn't feel confident