Should I use more than 5 gallons?

Hi all. I've been vegging five 4-foot, bushy Smurfberrys for about 2.5 months. I switched the lights to 12/12 a few days ago. I'm worried that the 5-gallon bucket will be too small during flowering. The only indication I'm getting about the root structure is that the plants get bone dry two days after watering. I'd rather not stress the plant by transplanting it, but I also don't want to lose yield if I keep it in the 5 gallon.

Any suggestions would be very helpful. Thanks in advance.

I've had similar concerns in the past and I found that cutting out the bottom of the bucket and placing it in a contractor's trash bag about 1/2 to 3/4 way full with dirt. It'll give a ton of room for the roots to occupy. It's an easy switch for the plant just watch the ph in the new soil. The bags can be raised or lowered on platforms of plywood and milk crates.

well if your plants are alrdy 4 ft, im pretty sure the roots have filled up every inch of that pot. I just transplanted a 2 and a half foot plant out of a 5 gallon bucket into the ground, and the roots filled up the bucket. i transplanted it by myself, and caused no shock to the plant, it actually grew taller the next day. if u want your plant to grow better it will be better off with more root space, but if ur not confident in transplanting it, fuck it. i have no other advice lol.