J330, I have flown the Skyraider Mach II and agree that it flys very well. I had a Thunder Tiger .40 in it with a 9x6 APC prop (it was setup for entry level pylon) and could likely hit about 100 to 110 mph. That is fast enough that the ailerons are close to wanting to flutter. For a sport setup, a 10x6 or 11x6 depending on the engine would be better all around. It has a good wing loading so take offs and landings were straightforward. If I had any complaints, it was not with the design - that is very good, but some of the hardware was not as good as a Sig kit would have, and some of the wood especially around the landing gear is kind of weak. So a bit of reinforcement there before it gets oil soaked is worth the time. I lost mine in a mid-air collision, but bought a second so I do think it is a very good design overall. They do use their own covering on them but I have seen several that were stripped down and recovered mostly for ID because having 4 identical planes on a race course is difficult.

There is no secret here about what makes a great second airplane. Unfortunately too many get bad advice or they get tempted by slick ads and shiny scale models of warbirds. After a new flier has 5 or 6 models under their belt, the loss of an airplane usually has little impact. But when they reach too far with their second or third model and fail, it seems like a significant number drop out.

If you have a model that has a tapered wing and a higher wing loading, you have to approach every flight with an awareness of a much more restrictive flight regime in mind, especially during take offs and landings as well as high g manouvers where a unexpected snap roll can lead into a quick spin into the ground. Altitude, knowledge of spin recovery, and the ability to recognize the situation and not panic are your only defense. Trust me, I've splatter'ed more than my share, but rarely on the first flight.

A few things I have learned along the way, and some that we told to me:

Never make the last flight
Never trust your eyes
If something doesn't seem quite right with the radio or servo, it's not
Don't fly downwind
Always do at least 5 touch and goes every flight
Always get a tail dragger tail up in the air and tracking before you lift off.
Always land on the main gear by bleeding off speed first.
Always check your batteries under a load before each flight.
Always check your hinges and pushrods before the first flight each day
Always range check before the first flight

If you're lucky enough to have a very good flier at your field, ask them to help you test fly and trim your airplane. When they have confidence in your flying they may let you fly their model. You will usually find out that half of the reason they fly so well, is that they know how to set up a model so it flies well. You can easily learn how to do this too.