The bass also has an intentionally twisted neck! It makes it a bit easier to fret octaves low on the neck. I made the neck on the CNC, and the rest of it with hand tools. I want to make another one, but haven't really played for a while. I learned/took lessons a few years back for bass, then guitar. I played quite a bit for a couple of years.
The biggest advantage (I think) for the line array style is that you can get a lot of volume for a low price.
Each of the woofers were $1.25 and the tweeters were $2. When the drivers are stacked, instead of a half sphere of sound radiating towards you, the spheres get squashed vertically. So instead of the sound spreading out vertically and horizontally like a single driver, the sound spreads out horizontally, but comes out vertically closer to a line. So you get 3db more sensitivity/volume over a single driver each time you double the number of drivers. So, even though one of each driver would not come even close to putting out enough output, 8 drivers will give the equivalent of 8x2^3 or 64 drivers. Is that right? 1 to 2 to 4 to 8 = 3 x 3db = 9 db. 10^(9/10) = 8. 8 x 8 =64. Wow, even I didn't realize that.
If you are far away from the line array for its height, the line array is even better since sound isn't wasted up into the sky and ground. For rooms that don't have ceiling or floor treatment (absorption), it can be a benefit too. My short ceiling height room is a good example.
The disadvantage is comb filtering, which comes into effect if the spacing between the drivers is large relative to the wavelength they are producing. This is because the sound is being generated by two or more different drivers and arriving at your ear at two slightly different times. This causes comb filtering which you can probably research on wikipedia, but I recommend the book, Master Handbook of Acoustics! It discusses that topic and others really well.
Great news on the THT. Looks like you will be able to use your plate amp too, which is a bonus. Are you going to do a build thread? It will be interested to hear what you say about the comparison between what you have now and the THT.