The isolation is the first thing I tried. It definitely helped, but still no solid 110 degC. I'm not an isolation expert, but these are the results I obtained.
The limiting factor is the RAMPS module at this point. I once tried 4x2.2Ohm resistors in parallel and the mosfet melted through the RAMPS module

To give some insights in my efforts:
Test1: 4x4.7Ohm resistors in parallel (default setup of Felix 1.0)
Each line adds extra isolation compared to the previous line.
- baseline, no isolation max temp 70 degC
- bottom isolation, only bubble plastic. to decrease convection losses on bottom. This increased temp of + 10 degC to 80 degC
- bottom isolation, bubbly plastic with alu foil for radiation. + 10degC to 90
- Encapsulating the heat resistors with silicone kit +2 degC to 92degC
- top isolation, aluminum foil. +13degC to 105degC. THis is unusable with foil on top, but gives insight in approx max temp with these resistors.
Test2: 4x3.3Ohm resistors in parallel. Had to include extra heatsink on mosfet to keep temps in check. So not a very safe situation.
- Temp without isolation 82 degC
- Temp with buttom isolationem isolatie 100 graden. When you start printing the temp drops to 94 degC
- Alu foil on top raises the temp 15degC. Up to 115degC
It got pretty close, I hoped a more efficient heater like the foil heater would do the trick, but it is hard to get good specs for it.