Back to the original question. When I asked Russ Ramirez this same question he replied:
Typically to get a dial on a receiver, signal generator, etc. you have an adjustable coil for the low-end of the band in question and a variable cap for the high end. In this case, the inductance is fixed and yes, the 560 pf capacitor can probably be increased a little to bring things in line. A 680 pf cap may not be excessive, but if it is, then another cap in parallel will be additive. If you happen to have a small trimmer cap to solder in parallel, that would be a good way to dial things in.
I posted this earlier but cutoff Russ' reply.