I was horrified when I looked at the spectrum coming from the minion on 80m so clearly a low pass filter is needed. I used the notes from GQRP on low pass filters for my design and it looks good when swept.
My build is not very compact and indeed it's almost the same size as the whole transceiver.
I quite like these boxes, purchased on AliExpress and plan to make low pass filters for 40 and 20m as well.
The filter on a spectrum analyser shows that it's 3dB down at 5.16Mhz and the first harmonic, at about 7MHz would be down 25dB at least.