Hi Nicko,
A couple of key points that I can think of off the top of my head when deep frying a turkey...
Don't buy a turkey that's too big. If you stick around 12 lbs you should be fine in most pots.
Use the proper amount of oil! This is a big one where people have a slight miscalculation on the amount of oil to use. Take the bird out of it's packaging, remove the innards, position the bird on the hanger (as if your going to be frying now). Now place the bird in the fryer and cover with water. Be sure that the water has sufficient room above the oil line with the turkey in place. Remove the turkey and be sure the water inside the cavity remains inside the fryer. Note the water line, after turkey has been removed, this is your fill line for the oil. If your brining your turkey you could pour this water into your brining vessel and add your salt, etc.
Properly filling the pot with oil is crucial, and a common mistake that can be quite costly. Be sure the turkey is dry, inside and out. You can position it so it's standing up on it's rear and leave it in open air inside the fridge the night before if you like. I usually give it a thorough paper towel treatment, inside and out.
Another big one is placement of the fryer. Be aware of your surroundings and any pitch there may be to the ground it's sitting on. If the perfect place to fry appears to be uphill, near some combustibles, well...it's not the perfect place. Give yourself some room and be aware the area will get oil on it. Also give some thought to placement of the tank and access to the valve. You want easy access to both of these and you also want to put them in the safest area if you do have problems. If something should go wrong, you will want to shut your primary fuel source off. But it comes into question if you can't do this safely...so give a little thought to placement of the tank as well as the burner/fryer.
Your frying an awfully big bird...with an awful lot of oil. I would always suggest using two people when lowering the bird into the oil. You have more control of the rate that you drop the bird into the oil...and you will have more stability should the bird slip or shift while your lowering it into the hot oil. When you, and your assistant, are lowering the bird into the oil GO SLOW! You may have to lower it in and hold it in position for a moment before lowering it more. After your done be sure to Place the top part of the hanger and the pole/broomstick in an area that is both accessible, and free of any oil splatter.
Before the turkey goes into the fryer give some thought to how your going to pull the bird out...and what your going to place it on when you do. Get a large pan (possibly a large roasting pan) ready and in place. You don't want the turkey to be finished cooking and your trying to get the pan ready.
When the bird is done, shut your fuel off and be sure the area is secure. You don't have to have armed guards standing around it. But be aware that the oil is going to stay quite hot for some time. You'll want to give thought to placement while your cooking...but also to that placement when your finished cooking as well. Put it in an area outside where you can still be social and have it accessible, but one that's also out of the way a bit too. If you can, keep it away from high traffic areas. You don't want people tracking through the oil splattered area and then walking around. It's a mess and it's a slipping hazard. Be sure that any children are aware that they should not go near the cooking area, even after the bird has been eaten.
Lastly, pay attention to the weather report. Right now they're calling for possible snow in our area. Obviously snow and rain are a deal breaker when you're frying. Another one that I've run into at work is people frying a turkey in their garage. Some people consider this an extension of the outside, and not part of their house. Should you have to tell people not to use a lp gas turkey fryer in a structure?
I know you're just trying to be extra cautious...But use commonsense, go slow and be aware of tank placement and valve position.
have fun!
dan