I have a 4 vessel (2 BKs) bottom drain setup that I have brewed on about 15 times. Three were cut upside down & I had a previously configured "top cut"HLT that I added a drain to.
I am running a single controller, a single pump, a removable HERMS Coil,haven't installed all of my temp probes yet and have a lot of little things to finish up. By not completing the system all at once, I will probably end up with a system that will require fewer changes in the future.
The HLT is a no brainer.
The MLT is easy to clean. I used the bottom cutout with slots cut by an angle grinder. With a reasonable flow rate and a return manifold, I haven't had any issues sticking. I used a bowl to transfer the used grist to a bucket, and then simply rinse the rest down the drain....it couldn't be easier.
I have only used one BK so far. I have been whirlpooling, and do not use a side pickup. Instead, I made a temporary pickup out of the spear housing, a washer and some tubing. It has worked pretty well so far, but I have left a little more wort than I wanted at the end of the boil a couple of times. I am debating on whether to also install a side pickup, or spend spend the time and effort to setup a plastic conical and just drain the trub after I transfer and let it rest for a while (I may also recirc with a hop spider to get some of the big stuff filtered before sending to the conical) Maybe I will do both....haven't decided. I use a copper "J" to transfer from vessel to vessel, and it seems to whirlpool without any problem (maybe I will add a whirlpool return if I start popping holes in the keg). I will tell you, that I when it comes to cleaning, it couldn't be easier.
The only downside on bottom drain: the way I did it forced me to commit to drilling holes in the stand and living with a CIP. If I wanted to change positioning at this point, it would be a challenge.
I have stolen most of my good ideas from this website. I couldn't have spent all the time and money without the "enablers" on HBT.