I would not recommend using straight Xylazine, no matter how heavy the dose. I have seen 5 1/2cc straight Xylazine(100mg) in a doe once and she still got up and walked away.
Could you use straight Xylazine(100mg) and have it work - yes, but I would NOT. It will be easier and safer for you and the deer to use the mix of Telazol/Xylazine(100mg) mixed as both Mikes stated, and 2cc should get the job done. It will at least take him down enough to be able to sneak up and syringe another 1/4cc to 1/2cc if need be. As already stated, individual deer will vary at times on amount needed.
Safer for you: Using straight Xylazine will typically put the deer down and give the appearance of being out, until you approach and up he comes and takes off. The deer has enough control to get away but not enough control to avoid contact with you should you happen to be near his front.
Safer for the deer: You will drastically cut down on the possibility of aspirated pneumonia, and they will not do all the stumbling around, going down, getting up, going down, getting up, all these things that can be indicative of using straight Xylazine.
Dosage on using the reversal Tolazine: I have always matched the amount Tolazine with the amount of Xylazine(100mg) used to put the animal down, and they are up moving around 8 to 15 minutes later, depending on how noisy or quiet it is during this wake up time.
There seems to be a difference in opinion on ''when'' to give the reversal Tolazine. I have tranqued well over 500 deer and have always given the reversal right away. I used to use Yohimbine(not a recommendation) but now use Tolazine. So since the switch to the reversal Tolazine, I've tranqued 175 or so. And all these 175 or so have received the reversal Tolazine as soon as I could give it(I've actually hurried to give it), and I've seen no ill affects, only positive.
I've only one more comment: Shame on those of you that did not use ''mg'' when prescribing the drug Xylazine. There is a certain somebody out there that will chastise you for your ''kitchen table'' prescriptions and lack of the terminology of ''mg/kg'', and if he sees your posts - look out!!! LOL
I'm sorry ''mate'' - don't take it personal - just havin some fun with ya - I believe in what you stated before, we really should speak in mg/kg.