I like my internal downhaul.
I have run into some trouble with the internal blocks bottoming out on the mast plate and then disassemble is nessecary to correct. What I do now is make sure I have the downhaul line that attaches to the block on the sail pulled
all the way out before attaching to the mast. I also had the internal shackle come unscrewd once. The biggest PITA
I found was getting the screws out of the mast plate, they tend to seize in there so now I lube on reassemble.