We made on special request a 40 meter HyEndFed. We tested it with 1200 watt PEP. We use a big Ring Core and a special Hi Voltage condensor.  Here you can see the end result.

This is a plot of the SWR of the 40 meter QRO HyEndFed. As you can see the bandwith is topnotch. It covers the whole 40 meter band!.
SWR may vary from place to place.