My first experiences with this board on 20m using a FT82-44 core are, that the core gets hot at 5W on 20m / 14MHz.
Based on this experience I consulted the mini Ringkernrechner and and did some calculations. As far as I understand, the primary coil with 3 turns limits the maximum usable power.
14MHz / 20m Band
The voltage of 19Veff equals to 7W HF and that about 1W is burned inside the core!
7 MHz / 40m Band
If we switch to 7MHz the core with 7W input is in saturation:
On 7MHz you can use only 3.5 W HF (=13Veff) from which 0.77W is converted to heat.
3.5MHz / 80m Band
Switching to 3.5MHz reduces the maximum power down to 1.6 W (=9Veff):
This gives an increase of nearly factor x2 for the usable power:
|Core / frequency||3.5MHz||7MHz||14MHz|