"I plan on putting the posts underground and putting them in cement."

If I am understanding this statement you want to install them like putting a fence post in a hole and filling around it with concrete mix. I don't think that will work with the angles and the upward forces would probably bulge the surrounding dirt. But if you want concrete you can put some Sonotubes in the ground at each leg and attach the legs with a post anchor. The Sonotubes can be sunk or sticking up to make the swingset level and all the legs remain the same length.

3onthetree: yes, i want to install like putting a fence post in a hole and filling around with concrete.

Can you explain the latter half of your response? Not sure I quite understand.

The longer legs go on the downhill side.

I assume you desire the concrete to keep it "in the ground" and from rocking and overturning. Consider how you will dig a hole in the ground at an angle, then fill with concrete around the post. And the rocking that causes the angled post to uplift. Probably not gonna happen this way.

So as a solution to your desire for "solidness" of concrete, you can use Sonotubes, which are circular cardboard forms, that you fill with concrete (but you can use anything to form a pier). You set a steel bracket on top, which the post is then fastened to. This would allow keeping same leg lengths (or you can still have different lengths). If the time comes for the swingset to move, the concrete is still there and would need dug up.

You can also decide not to use concrete at all, so you would need different leg lengths and just use a ground screw anchor. This is sufficient for most people. If the time comes for the swingset to move, the screw anchors can move with it, but the differing leg lengths would need adjusted.

suedonim75 - I looked into this, but read these aren't as sturdy/safe for kids who like to swing high/hard (which my 4.5 yo does).

I will re-post asking advice regarding this project. Thank you for all input.

Why would you re-post?

Now I"m not even sure which type of swing set to use - A frame or non-Aframe (like the one you posted). Thought re=posting would provide a more concise overview. Oh well. Will continue on here.

1. Which is the best shape/configuration for what I need? Non-A frame or A-frame? (I read online the non-A frame isn't good if your kid likes to swing high).? My 4.5 yo likes to swing high/hard. Is this true?

If Non-A frame, can I build myself or hire? How thick should the posts be? How long?

2. If A-frame is the best, do 2 of the legs need to be longer (12-18'') to accommodate for the slope in the yard? If not, (if all legs can be equal), what is the minimum length the legs need to be to work?

3. Should same method be used to secure either configuration? (with sonotubes) as suggested above?

I would put the swing set below the grassy area where it is flat. Otherwise, I would hire a pro who knows what he/she is doing.

I appreciate the input from individuals on here

Thinking of doing the following:

Use 6x6 post (non-A frame style);

Dig hole below freeze/frost line

Use sonotube. Put a cast-in base post plate/attach to 6x6 --> pour concrete in sonotube? (do you first pour concrete into the hole, then put the sonotube in, put the cast-in base post plate in, then fill sonotube with concrete)?

Here is a video showing the CAST-IN BASE POST PLATE https://www.youtube.com/watch?v=95_jg0Hms1s (1:20 in video)

Think this should work/be strong enough?

If you do the 2-post version it should not be attached on top of concrete piers at grade. That connection would be your weak point. Observe a municipal street light and the connection at the base to keep it from tipping over - your typical Simpson anchor with just 4 main screws at the bottom of the post will not resist that 'overturning force' from two possible maniacal swings. Simpson does however make a moment (the 'overturning force' resister) post base but they are ludicrously expensive and still may not stand the test of time with the post splitting and checking. With a 2-post, the posts should be buried and then they will use the depth in the ground to resist the 'overturning forces.'

My suggestion of using a Sonotube (dig first, place tube, pour concrete, then insert anchor on top) was a solution to your desire for concrete with an A-frame.