If you are using an airstone that can clog, you do need to worry about high pressure. My input line is open ended and the only pressure it sees is the pressure of the waterpump powering the DIY Vortex reactor, not much, maybe 6inches of head, whatever pressure that calculates out to be.
If you get high enough pressure in a DIY system to worry about a plastic bottle then you have other worries as well. Something along the lines of "I forgot to drill a hole in the cap and insert the tubing" problem. Or the old "I put a large weight on the tubing problem", as long as the system has somewhere for the CO2 to go then the pressures are going to be very low.