Here you go...
I have traveled with a guitar in a plane a couple of times (4-5) and twice with a guitar+ single pedal... and always the guitar was the cabin baggage.
The guitar is a strat copy, and it had a largish well padded ibanez soft case (
http://www.muzikenstrumani.com/resim_goster.php?pid=2802&title= ) with couple of pockets that I was using actively while traveling. It normally fit the overhead. Yet once I boarded the plane very late and there were no rooms in overhead storage so the crew put it in a place where they had their own suits and bags.
The planes I have flied with had either 2-2 or 3-3 seats on sides. The planes used in Europe. Yet I am not sure with the smaller planes like 2-1 seats, which operate like buses in Europe.
On the other hand my girlfriend flew with a large ovation acoustic in soft case in overhead over Atlantic (without any pedals). And I have seen a taylor or martin jumbo with hard case flew in overhead (again) over Atlantic.
First time I was also curious about it, and made a research of my own. There were couple of people who were telling that we should directly ask for the cabin crew whether they can put the guitar in their own storage...
My final thought is I do not think pedals will be a problem but as previously said home-made pedals might be suspicious. As for the guitars, a solid body (not something large but a strat,tele, lp or sg) with a hard-case should not cause any problems (my case was certainly thicker with the pockets full). But in case you might bring a simple soft-case and put the guitar overhead with soft-case+ your coat.
And the companies that I have flied with a guitar were lufthansa, SAS, norwegian and sterling (not operational anymore)
Hope this helps...
And do not forget once they check you, they try to find somewhere to put your hand baggage.
