its isnt really possible. however, what i do is simply turn the qualifying time down to 15 minutes and there's generally a mad rush to set a lap. if you keep the number of consecutive laps as default (in gpxpatch) sometimes you'll find some of the drivers will be really pushing it to even cross the line to start their lap before the chequered flag comes out. this is kinda cool cos it gives the effect of the knock out system when you see some of the big names starting near the back, because they couldnt set a lap. this usually only effects one or two cars generally. makes for exciting races too.