I had a 4' Sputnik and I fed my YBs in it on a large aluminium tray, you can get your YBs hand tame quite quickly if you hand feed this way.
Race days I'd make sure I had about a min of 10 YB in the loft.I'd stand inside calling the birds whilst feeding the YBs on the tray the Racer would drop in. I'd pick it up remove the rubber and put it back down to continue feeding, it wouldn't even know it had been clocked.
Get your YBs onto peanuts (human grade) if you want them really hand tame. Also I would always put the YB through the sputnik before I let them out for the first time, pigeons can be so stupid sometimes.
I'm now on ETS.