Luke shouldn’t be any taller than 11.33 inches or 28.77 cm but we all know that HT isn’t consistent with its heights or scale.
3PO shouldn’t be any taller than 11.66 inches tall or 29.21 cm. The Tamashii is 11 11/16” or just shy of 11 3/4” tall so your 11 3/4” assessment is correct.