Not sure if this is the right forum, but i’ll post anyway 
Is there a good, light and functional solution as how to flyfish while drifting down a river. Do you just lay your rod down on the spraydeck or are there any smart solutions/rodholders out there?
I reckon you’ll have to sort out what works for you.
We use a raft to raft out after our wilderness fishing trips in NZ, but haven’t needed ,or wished, to fish whilst rafting.
I’d probably just put my rod on the spray deck, and have a paddle leash, and hope like hell there was no white water to negotiate whilst trying to hold all this together! I’d also make sure you don’t fish a sinking tip, or beaded nymphs - the former likely to hook you on the backcast, and the latter more likely to hook you on the forward cast.
Ultimately I think I’d rather fish from the bank, and use the raft for travel.
i’d fish from the bank and use it for travel to fishing spots. reel up and tuck the reel down by my side pointing backwards and paddle. i would only use the packraft to fish in a lake.
Thank you, I’ll see what works best for me 
For lake fishing, specifically, we do see quite a few folks like the Dory Seat in a normal raft, so they get some extra height.