Re size - My vet just makes sure Cat is over a year old and after that I think most cats are similar in size/weight. If the cat is excessively small even though it's older then a year then I'd just mention it to the vet - being a wild cat i don't imagine that it is very heavy!. Sleeping tablet is just a quick solution which I've never had any problems doing - as it happens I think it's quite a humane way to do things - what's to say the cat won't go into a huge panic when trapped and then put into a cage in the back of a dark van?. I know my cat has an extreme fear of travelling, the vet specifically told me not to put the cat into the car until it was drugged as it was terrified, cat soiled itself, cat box and vet and the vet then couldn't calm her down enough to do an examination.