I'm quite enamored by 1x systems for simplification of drive trains and have converted 2x and 3x cranks a number of times. I don't have a problem with chain drop after removing the FD even with 8speed cassettes.
This is a 3x to 1x8 using a 42T chainring in the middle position. The bash guard is the original large ring ground down and the inner granny ring is there for a manual shift bailout if I need it. This meant no added washers or adjustments.
This is an old 2x5 ten speed converted to a SS. I just took the old school chrome chain guard and large ring off.
An 84 Diamondback
Ridgerunner 3x7 converted to 1x7. Again just removing the outer and inner chainrings. You have to add washers to the remaining chainring to make up for the lost width from the outer one when bolting to the crank arm.
In this case it actually became a negative cost, or cost savings, as I used the now unneeded nice Suntour friction thumb shifter for the FD on my next build which was also a 1x. Note no FD's or chain guides. This is because I usually use the middle chainring position which is designed to run up and down the whole rear cassette without cross chaining. If you use the large or low chainring the chainline may cause the chain to drop.