Setting up a pressurized CO2 system - got lots of questions

[spilzer]

Hi everyone,

So, I finally decided to bite the bullet and setup a pressurized CO2 system for my 29 gallon planted tank. I've been researching it for over a year now so I'm pretty sure I understand the theory behind it, but I'm worried about making mistakes when it comes to reality.

Here's what I think I want/need:
5 lb cylinder
reactor/diffuser
brass check valve
timer
drop checker (maybe, I know this isn't necessary, but it sounds like a nice accesory to have)

Here's what I already have:
Milwaukee MA957 CO2 regulator (complete with solenoid, needle valve and bubble counter)
some CO2 hosing that came with the regulator

My questions:

1.) I have a few leads on obtaining a cylinder but I am wondering about safe practices for transporting a filled tank on public transportation. I live in NYC and don't own a car so I would most likely be bringing my filled cylinder back from the shop on the subway. Do you think this would be a problem? I've read some horror stories about cylinder saftey valves going bad and exploding tanks which makes me nervous about carrying a potentially dangerous item on the subways. What do you think, is it safe to travel on the subway with a filled CO2 tank?

2.) It also looks like I could order a 5 lb cylinder online at aquariumplants.com for $49.99. They will also ship you a filled cylinder for $89.99. I know that's a lot to pay (it's due to the extra work of shipping hazerdous goods) but I was thinking it might be nice to have a pre-filled tank arrive on my doorstep. What do you all think, is this a good idea, or should I try harder to work out something locally?

3.) I have a canister filter and I've heard I can use that as my reactor. I'm worried though that the CO2 might 'cause a airlock effect where there was a dry spot in the filter that could damage the pump. Or that it might break the siphon in the tubing. Has this ever happened to anyone? If I do want to use the cansiter as my reactor do I just splice a the CO2 tubing into the fiters tubes or should I place it in the tank so that the bubbles get sucked up into the filter intake?

Thanks in advance for your advice. I'm hoping to get started on this project next week when I'm on vacation. I'll post pictures as I get the pieces set up.