ECB

Hello I'm 16 and have been Kamado cooking for about the last half year, but haven't done loads of cooks and am very inexperienced! I've got a couple of points that need clarifying (although they probably have already been discussed somewhere else on this website!) Every fortnight I often cook about a 3.2kg beef topside on the Kamado. I'm not sure whether it's just that I purchase really cheap joints, or whether i'm cooking it wrong, but it never really ends up as tender as I wish it to be. The flavour is awesome, but the texture isn't great... Am I right in thinking that rare should still be tender and moist? I often take it off at about 57 - 63 degrees C and then leave it to sit wrapped in foil for at least an hour. What am I doing wrong? Also would appreciate any other helpful tips to increase my knowledge of kamado cooking!