The space this is going in is only about 100' long and 45' wide so it should fill the room nicely.
Then you need to be making at least 2 T48s. Horns work best in herds of 2 or more. Want to maximize output? Build 2, 36" wide T48 and load them with the 3015LF. By using a driver that is half as much $$$, you get twice as much sound. Study the placement sticky
and follow it as much as you can.
I don't think we'll be over driving this particular Lab15 as it's only going to have a max of 650watts running to it from a little Crown 1005 setup in mono with the LPF set to 100hz. The space this is going in is only about 100' long and 45' wide so it should fill the room nicely. Currently there are just a couple EVs flying for sound in that space and the low end is pretty much non existent when it gets crowded (100 people). So portability isn't a concern, but hitting the low frequencies is a must hence why I'm looking for a low Fs and high Vd. The more air you move the lower you can go....generally.
This whole quote tells me that you are very inexperienced in running a sound system of any magnitude, meaning more than 2 trapezoid cabs on sticks. We all started there. Read this entire forum. We will not bullshit you, or pass along false information. We WANT your build, and you, to succeed. There is so much experience on this forum, willing to teach you the scientifically proven ways to maximize your results. All you have to do is listen, and follow the advice. It is a leap of faith, but in the end, it is an education that you can use until the day you die. But, we can only lead you to the well, it's up to you to drink.
Since this is for an install, tell us what you are trying to achieve. Be as specific as possible. A 100' x 45' venue will hold a LOT more than 100. Are you doing dance parties? What kind of music are you playing? Top 40/Pop, EDM, Hip-Hop/Rap, Modern Rock, Classic Rock, New Country, older Country,etc...
Do you understand that EQ, an electronic crossover and a hard-knee limiter are MANDATORY for any PA. The one good thing in your favor is that once the PA is set for the room, unless something in the room changes, you won't have to change it.