Roger wrote:
150 kts cruise at low altitudes (less than 8000 ft) at less than 65%
power (don't like running the engines hard) and less than 18 gph
(don't

I'm firm believer in running those big engines at 75% and don't
believe running them less is doing them any favors.

Then we'll agree to disagree. I think 65% or less and LOP is the way
to go. 1500+ hours, and only replaced 1 of 8 jugs.

You said 4 full size adults. Today that is 4 X 170 = 680# (if you
are
lucky to find 4 trim adults) plus at least 20# each for baggage makes
760# after fuel.

A plane that can put full size adults in every seat and still fill the
tanks has tanks that are too small. My normal mission is 2 full sized
adults, bags, and full fuel for long range flight. My alternate
mission is 3-4 adults, light baggage, short range. I adjust fuel load
accordingly.

My normal launch states are full tanks (allowing me 600+ lbs of payload
and a 5 hour endurance) and mains only (allowing me 800 lbs of payload
and 3 hour endurance).

At 9 GPH at 65% you are pretty much talking 4 cylinder engines. Even
an IO-470N will run about 12 GPH at 65%.

No argument. Both my certified choices feature small fours.

But figuring your optimistic 18 GPH @ 5 hours plus a half hour
reserve
= 99 gallons useable so figure at least 110 to 120 gallons @ 6#/gal =
660 to 720# plus 760# for pax and baggage means about 1500# useful
load.

Remember I said my plane does better in all respects. For me, 150 kts
happens at 15 gph at 8000, so my 90 gallon load is plenty. Also given
that with full fuel I only need to carry 2 adults and bags, we're down
to about 1200 lbs useful load. But of course with less efficient
airframe/bigger engines it might need to be more.

The hard part is going to be getting it all together. The hardest
part is the speed at 65% at low altitude loaded and that fuel burn.

Not hard at all. There are two certified twins that meet my
requiremens, and either can be had in very good condition for less than
$100K. Those twins are the Beech Travel-Air and the Piper Twin
Comanche. The Twin Comanche is somewhat more efficient and has cheaper
parts, but is more demanding to fly.

Anything smaller has miserable single engine
performance.

I only need a 5000 ft absolute ceiling on one engine at gross - my
flying is almost all in the lowlands. Therefore, I am not concerned
about the miserable single engine performance. Actually, when you
compare light twins at full gross, they all do just about the same
until you get into the cabin class.

Get the Geronimo conversion, put 70 grand into a new panel...well
maybe 80 grand and you'll have your machine...except for the fuel
burn
and easy to find parts.

I already have my machine - and it meets all my specs and then some.
Unfortunately, it is certified. If I could have an experimental I
could buy (not build) to meet those specs, I would pay up to 50% more
up front to buy it than I paid for the certified airplane.
Unfortunately, it's not there at any price.

Michael