Quick questions on what everyone else is doing

I'm up and running and with my BCS electric brew system. A couple quick questions to other electric brewers. Things I did not deal with in Propane.

#1. I have a 4500w ULD in the BK. During boil, what does everyone run there element at? 100%, 50% ? I am running at 65% once at boil.

#2. I have a copper immersion chiller. Is it OK to place in BK on top of element touching it? Or do I need to make a spacer.

#3. I am doing full water recirculative mash where I calculate what I want in the BK and work backwards. Adding back grain absorption and loss. This is what I heat up and hold for Mash. I then bring up to 170, hold and transfer to BK. Sound right?

I have a similar system controlled by a PLC. My first brew on it I was similar to you--ended up running my 4500W BK element at 70% boiling 12-13 gallons. I throw in an additional 2000W heatstick during initial heating, but pull it out when it gets close to boiling. I have a HERMS coil in my HLT that rests somewhat on its 5500W element, like your BK IC situation. No issues so far, but long term, I don't think you want too much lateral pressure on the element. Probably need to consider legs to support from below or some way to hang it from the top. I also have a similar set up for the mash and sparge water. I use Promash to calculate water needed and batch sparge. Ended up with an extra gallon into the BK after the last brew, so I have some tweaking to do on the numbers. Overall, your approach sounds pretty typical.

I'm working on legs for the IC as I type this. Easy to do.

As for full boil loss, Im still trying to get that number but I'm close. I have grain absorption, trub down from old system. I guess I need to brew more to perfect this system.