Since we're on the subject of engines and I'm another 173RG IO 540 guy, I thought I'd put my two cents in the hopper.Mel Ball is flying his and I'm not but my engine is mounted. I have the 260 Hp parallel valve engine that weighs 405 lbs. Alan Shaw built my cowling and had my engine mount made as well. The latter is so designed to bring the engine as close to the firewall as possible for CG considerations. I had to purchase a B&C oil filter adapter before my engine would fit. My 540 has the Bendix fuel servo mounted on the bottom using an elbow adapter so that it faces forward.Alan's cowling is beautiful with the top portion looking like the hood of a '57 Thunderbird. The lower portion has to dip down below the standard fuselage bottom by about 1 1/2-2" (to encompass the engine completely) in the center which is somewhat disconcerting at first glance. Velocity has fashioned a male NACA from a Camaro which is part of the standard XL installation. I used one of those but built up the aft portion of the lower fuselage around this NACA until it became a female NACA which provides ram air to the fuel servo. So the new lower aft circumference of the fuselage is now flush with the bottom of the lower cowl. I think it looks good.I have kept my front oil cooler and installed a wing root oil cooler as well which I intend to connect in series (with the nose cooler receiving oil first for heating purposes). Because of the distance the oil will have to travel I have used the 5/8" OD steel braided Teflon hose for this purpose.My engine came from Don George. As has already been stated, so far I have nothing but good things to say about their service and professionalism. It is interesting that a 540 cost nearly the same as a 360 because the demand for the 360's has made them more difficult to obtain and thus supply and demand issues have narrowed the cost differential.The big issue all along for me has been the CG. I have fashioned an epoxy/buckshot composite piece to fit in the nose above the landing light which weighs thirty pounds. If I have to trim some off, I can. Somewhere, I read or heard it said that each 10 lbs. placed in the nose moves the CG .65" forward. The engine is already snugged against the firewall. I intend to conscientiously abide by appropriate CG restrictions for my airplane but Alan has convinced me that I can do this with the 540.With all the recent tragedy, contemplating a none standard engine and/or propeller installation is sobering. My plan is to install everything else in a standard fashion with standard aircraft quality equipment that has tried and true track records in other applications.I can't say that my choice is any better than any body else's but I obviously believe that I will fly a safe and dependable aircraft. It probably won't go much faster than anybody's but maybe it will have a nice cruise speed at higher altitudes and maybe it will climb a little better than some.We'll see.Ralph Robertson173 RG