I made it work once in a test with the 5km range, but it's rough, and to be honest, not something that we should have to deal with. Probes and other 'live' objects shouldn't unload ever. Like, if Kerbals were on-board, they shouldn't unload.
This is EXACTLY what I'm trying to do right now. Been googling and searching, and searching and googling to no avail. I've got a mission to collect atmospheric pressure data from the surface of the water in the middle of the ocean. I've also tried lazor and found exactly the same thing you have, that probes unload before they can land. Lazor systems only ups the unload distance to about 5km in spite of the 99.9km the 'view distance' setting says it should be. I'm so incredibly frustrated right now. It would also seem that you've exhausted every resource that I've already googled for, and found exactly what I have, that nothing like this has existed since spaceport went kaput. If anyone out there has any answers PLEASE come forward with them. This is driving me insane.