I used both the T5 and the LEDs this grow. Part of this regime was because I got lazy. They were kept in Solo cups for too long (and suffered for it). I started them under the T5s in solo cups and had them under the T5s for about 3 weeks, then transplanted them and moved them into the tent under one LED. Sometime before I switched to flowering (a week ago), I added the second LED. I have a 2' 12 tube T5 that has become my favorite T5. I doubt that I will ever quit using it. Even with the LEDs, I see myself starting the plants under the T5. Also if your 3 x 5 tent is actually only 30 x 58, then it isn't 15 sq ft and it isn't just a sq ft smaller than the 4 x 4. The area of a tent that is 30 x 58 is just 12 sq ft--so it is 4 sq ft or 25% smaller. I am thinking that you use the #3 pots because of the way they fit into your 4 x 4 tent--you must have pots actually touching one another. In a 30 x 58 tent, using the same pots, you will have room between the plants and the walls of the tent--space not taken up by plants. Most of how many plants you can get into a given space is dependent on the size and shape of the pots. I have some 3 gallons plastic pots that have a footprint of a bit under 7 x 7, I have some 3 gallon smart pots that have a footprint of a little over 9 x 9--same amount of medium, but quite a difference if I am filling a tent. I find the smart pots also spread out a bit larger than the stated footprint of the pot. And they all have some kind of container that acts as a drip tray (I am partial to dollar store plastic dishpans). Also, as a side note, remember that more plants does not necessarily mean more bud. I had 14 plants in my 4 x 4--8 of them were reg seeds and unsexed. I have pulled out 3 males so far and feel way better about the tent with fewer plants in it. However if you want to absolutely fill the 30 x 58 tent, you might look for pots with a footprint that fits well into a 30 x 58" space. Three gallon pots come in all shapes and sizes.