Nice kit panu.rantanen. Sounds like you're much more comfortable with your LP style axe. And the Boss' Katana 50 is one of the most frequently endorsed home practise amps. Chris S sings the praises of his, approbation I take serious note of. If I was first buying hands on experience blind, and I was at the time I bought my first electric amp, after researching I'd have narrowed it down to choosing between either it or Blackstar's ID:Core 40. Hey, I did!

Yes open F is a PITA, though as I recall it was easier when I was younger. But that could just be nostalgia? You'll get it down in time with practise. I have deficits now in my left forefinger from neck surgery which makes the two string forefinger bar particularly challenging, and I have. Even I surprise myself with the speed at which I can transition to and from it now and yet still sound all clean before, on, and after chords, even more all finger big move more difficult ones e.g. F to B7 as in rhythm during the chorus key change for "You're Gonna' Lose That Girl" played in original key of E. I alternate between playing it using all barres except B7 if on electric, but all opens on acoustic.

A vital chord though. Although there are alternative voicings, nothing rings quite so true on acoustic as the open form, particularly when used in conjunction with other open forms. An essential chord for rhythm present in [u]a lot[/u] of songs. A useful and pretty progression to help nail it is the C-Am-F-G for four bars and then alternate it to F-G-C-Am, ....rinse and repeat ad infinitum until finishing on the opening C key chord. 50's style Doo-Wop it, rock it!, lotsa' tempo and rhythm flexibility which fits it to maintain interest and develop technique.

Cheers