Weight issues

Wondered if anyone else had any problems with keeping weight on their munsters. Evie is very skinny and hasn't even reached the 20 kg milestone yet despite eating masses of food. When Christine and Raymond saw her they recommended giving her raw chicken wings which I did but this resulted in her having a bad dose of crystals in her urine. I have to keep the balance of protein in Evies diet well controlled otherwise she has problems. She has had lots of investigations including bile acids to check for a Liver Shunt and everything is normal. She is going for a scan on Friday just to check all the internal organs but it appears that there is nothing wrong. So could it just be that she burns off more than she stores? If so does anyone have any advice or experience as to how I can get some weight on her or whether I should just not worry about it. Apart from the problems with her weeing she is incredibly fit and healthy. Lin - how is Ghillie doing now?