It is not likely that file size is the problem. If your preset is above the 2mb file size limit, then there will be a red message that pops up in the User Panel area where you upload your presets to the sync. That Preset Texture Format/Shrinking Guide is only for people whose presets have exceeded 2mb and want to learn how to be able to shrink their pieces down to fit it into 2mb.
One thing to make sure, if you and your friends have already restarted the game, is to make sure that whatever case (lowercase letters or uppercase letters) your preset filename is, make sure you are logging in with those same letter cases.
For example. If I export a preset and it shows "morgra_1.fhp" and I sign in with my username as "Morgra" when I login to the game, my preset will not show up on me to others.
But, if I export a preset as "Morgra_1.fhp" and I sign in with my username as "Morgra", it will work.
Note: If you have a compound name, with more than one capital/uppercase letter, this still applies. Make sure the way your preset filename username looks is exactly how your username when you login to the game looks.
