Royals all grow at differing rates, some saharans grow way faster and others are quite pokey about it. I have currently a two year old rescue whom is just 800 gm and a second rescue whom was wild caught whom is very slow she is 3 now and 900 gms. My 1/2 saharan male mojo is just a year and a bit and he is 1600 gm. 700 seems a bit small to me but not really small. He sounds fine.
Typically males and some females will hit the 700-1000 gm and stop eating for a bit sometimes a few weeks sometimes months at a time. Personally I pre scent the room if they come out and seem interested I'll offer if they don't I don't bother offering at all. That would be an advantage to F/T you might try pre scenting with some litter and if yours seems interested dash out to the store and pick up a feeder and hope it doesn't become a pet.