+1 on the 109 G2. Excellent way to make perkies. Also try the A6M2 for close-in fights off a CV or whatever, or the 190 A5 when you're flying over to a furball near an enemy base. There are mad perkies to be made flying some of these 25 or 30 ENY planes. Some other good suggestions would be planes like the P40, or the KI-61. Part of the problem you have is that a C-hog or Tempest or whatever is costing you a week's worth of perks. If you'll move away from the 5 ENY rides this will change. You should be making hundreds of perks per week, not single digits.
People who have been playing this game longer than a few days or weeks usually don't have a problem being aware of when the plane they are flying is a perk ride or not. But I have seen fairly experienced people go into, say, the Midwar arena and fly a plane that is perked in that arena but is not perked in the Late War arenas, not realizing what they were doing. The Spit 8 is the prime example. I saw a guy lose several Spit 8s in a row in the midwar arena, and never realized he was barfing up perkies each time.
I can see the logic in a message in your message buffer stating how many perkies you just spent upping your current ride.
ps: +1 on being annoyed when the perk price swings radically while in-flight. I recall upping a 262 once when it cost like 140 points, and after I landed it I looked and the price was up to like 240 or so. At the time, if I'd died at the higher cost, it would have left me with a negative perk balance. I land most of my 262 flights, but it only takes a loss once in a while to burn through the perks, and on average I'm just barely keeping my head above water perkwise.
