Unsure about form in slow movement

I've written the first 16 bars of the piece. It's all is in the same key(f major) so far, I'm now unsure what is the proper form for this movement(its a slow cantible like movement).

I was thinking of 

1. Ternary, like having a another a 16 bar b section then 16 bar A1 section, I'm wondering if that is a bit too long a section maybe 8 bars instead.

2. Rondo, because this seems like the most common for a slow movement 

3. Rounded binary form, it does seem natural to repeat these 16 bars, then have an 8 or 16 bar B section and then 8 or 16 bar A1 section and repeat them both

4. Or really lots of other form ideas

Anyway I'm unsure what is right, please gives me tips what is the right form for this movement?

most slow movements are more ternary. ABA coda. a good example would be the slow movement of Beethovens pathetique sonata. and its easy to vary the ideas from the first section just develop a triplet for the repeat and add a little more complex parts.

Spend some time really building towards a climax, whether that's textually melodically or harmonically is irrelevant. 

A lot of them are also in a more rondo-like form, like for example the second movement of K 545 by Mozart or the Romanze from Eine Kleine Nachtmusik.

Different forms might yield different expressive results. It is impossible to respond what to do when we can't se what you have composed, nor what you want to achieve with it. What matters is that you look/listen to what you have written, and decide what should produce the result that pleases you better. 

After all, you're the composer and you're the one to call the shots. I just hope that whatever you decide fits whatever purpose you have in mind.