Thank you for this post!
My experience:
Wouldn't start with current servers. No error info. I tried it on a FRESH FTB IE 2.4.2 setup, and it worked! I copied my world over, and it still worked!
No more "can't keep up" messages! It's not even pegging one core. All the load is balanced.
Backstory:
After I upgraded my cloud server to 4x3.2GHz Intel Xeon and 4GB RAM with SSD storage and still failing to run FTB IE, I tried a local server. I've spent the last week trying to figure out how my new 4.5GHz AMD server couldn't handle FTB Infinity Evolved for two people. It was crippled by being single threaded. I tried every Java option, and it wasn't enough. I have a much more powerful 5GHz Intel machine, but it's ridiculous to think MC can't work on a brand new 4.5GHz AMD CPU. I even tried to see if VMware ESX would allow me to assign 4 cores to one vcore (it can't) to solve the problem. I found out about Cauldron, and this post provided everything I needed to get it to work.
Thank you! And, thank you for hosting the files just so I know I had exactly what you had to get it to work!
Setup:
OS: Arch Linux (4.4.5-1-ARCH #1 SMP PREEMPT Thu Mar 10 07:38:19 CET 2016 x86_64 GNU/Linux)
Java: jre8-openjdk 8.u74-1
AMD A10 7870K @4.5GHz
16GB DDR3 2400
2x120GB SSD