Great Plains Solid Stand 1500 and orchard grass.

I’m about to attempt a fall seeding of Timothy and orchard grass. Im putting the Timothy in the grass seed box and the orchard grass in the big box. I can never get my orchard grass rate to come out right and there is no chart for it. Does anyone here use this setup and can they get me in the ballpark? I’m shooting dor 5lbs an ac of orchard grass and the drill is on 7.5 centered

Great Plains Solid Stand 1500 and orchard grass.