i have a 31/2 yo standardbredxtb/irish cob, he has nearly 10" of bone and is 17.1hh he weighs just under 500kg but doesnt look skinny
does that sound right?
I was going to say he sounded a little light til I reread and realised he was a youngster. If he looks well then I wouldn't worry. Far better for him to be on the light side than too fat
Are you using a weigh tape, the girth x length formula or a weigh bridge?
Weigh tapes can be out by quite a lot, especially with young hrose or cobby types.
My cob was 100 kilos more on a veterinary weigh stall than by weigh tape.
They are useful for moitoring wieght gain or loss though.