That's way too much dude. Benzos and alcohol can be a good mix as far as euphoria goes but its extremely dangerous. The biggest danger is not the drug itself but what you do while under the influence as benzos and alcohol can make you throw caution to the wind.
I hate to even tell people how to do this safely because it's like telling white people how to use the N-word around black people safely. Its possible, some people can get away with it more than others, but overall the rewards seem greatly dwarfed by the potential havoc. Since I know you'll probably do it anyway here's my advice. Keep in mind I have family members combine these daily.
No more than .25mg Xanax and 3 standard drinks consumed slowly. You should be around people that will keep a good eye on you. Especially your first few times. It's like taking acid. You can do it without a trip-sitter but you won't know if you need one or not 'til its too late.
I wouldn't worry about ODing. I would worry about the much more likely and under-emphasized rampage-style blackout this combination creates. This is not your ordinary blackout. It can lead to very eccentric and non-sensical behavior. I've found myself doing things not only that I would never do, but that I can't even understand the motives the next day. Here's some example of things I or my friends have experienced.
1. You have long phone conversations with family members which consists of either angry shouting or dumping out your darkest secrets and deepest thoughts. You don't even know what you said till the next day.
2. You decide to cook something. You either end up ruining your food and having to throw it out or setting off smoke alarms and sprinklers
3. You wake up and find you filled a few glasses, a trash bag, your bed, and your rug with urine. Your rooms smells like piss for days and despite your best effort you can't stand to even be in there. You end up exiled from your own domicile.
4. You go buy $30 worth of weed on credit and smoke it all. You don't even like smoking that much and you never get shit on credit. You don't remember the fun you had\didn't have. And now you owe a drug dealer money that you have no way of coming up with.
5. You show up to work the next day and get sent home before you can even clock in. This sets back your promotion a solid month and your damn sure can't ask for the raise you deserve.
There's plenty more. I'm sure everyone here has a story. Some of them are worse than others. I've heard the combo called the jailhouse cocktail and for good reason. It also leads to lots of hospitalizations and accidental deaths. Yes its an enjoyable and relatively cheap high. But its not that great on the scale of things and there are plenty of more enjoyable substances that are less dangerous. I would recommend you read erowid and find something better and safer to try or don't try anything at all. This has bad idea written all over it.