If you only want guild mates to take the spots (and they're not in a swap group) then it's selfish to decide no one else should be able to contribute. This mentality people tend to develop of "someone outside the guild has put in for the lowest possible contribution spot.... Quick, everyone rush to push them off the position!" is quite frankly destructive. It limits the spread of wealth to within a guild. The game flourishes so much more when wealth is shared between players then just trickled down. This is pretty evident within a guild that builds up its members. I'd much rather contact the outside player and ask if they wish to do a proper swap in exchange for more going into my GB so the spot is secure then only thinking of myself and asking other guild members to push them away out of spite.
Honestly, I'm a bit guilty of that. I usually fill my top 3 spots with my guildmates with 1.9 (I'm Arc 80 owner) right after my collection time. Then I leave the GB open with 4th and 5th during rest of the day and see if someone wants to get one of those. If a guildie donates at least 1.9 there, I just let them have it if nobody gives more until the collection time, same if I make an arrangement with some from my friends list.
However, if a friend just hops with 1.9 without a proper arrangement, I just get someone from our 1.9 thread to push him out. If he donates a bit more (let's say over 40 to 20 FP spot) I leave it to them. Same with neighbors, but I'm willing to push them out even way more.
TL;DR I don't mind giving my 4th or 5th outside of my guild, but they need to pay more than guildies if they want it.
Back to topic though, I have simple advice for you. Get blueprints in advance, stop donating your FPs and just focus on self-leveling your Arc. That way, disconnect it all you want, there is nothing to lose. Easy.