I don't usually fly them in game quite that heavy...75% fuel for me. If I understand right you're losing altitude at the Max Cruise setting? You shouldn't be. The real life B-24 is a booger to get up to speed and keep trimmed at speed. She is very unforgiving of hamfisted elevator use -- you can bleed off 15 knots and never get it back if you don't fly her the way she wants to be flown. (But that could be handy if you're a bit fast on final -- just pulse the stick aft then back to neutral -- there goes 5 knots -- works on the B-17 also)
When you level off leave the power at 100% until you've accelerated to cruise speed, then reduce to your cruise power setting. In the B-17 with 6x1000 or 12x500 and 75% I use 2300/38 inches for cruise without any issues....have done that up to 25K or so.
With the B-24 we flew at 30"/2000 RPM, in the B-17 we used either 28/1800 or 30/2000 if in a hurry. We were low and lighter than a wartime airplane, probably the heaviest I flew the B-24 was around 53-55000 pounds. At that weight we used all the runway taking off at Naples, FL.
Very cool video! I've never flown in anything but a helicopter and eventually I'm gonna fly in a plane. Looks like a blast to fly something like a B24.