@10, getting 100 more SP and and 300 more phys then Bronze Squares @ 9, (same "suggested level" difference) Imagining this is much closer to a 15 synth or so.
I was doing this at 11 with master forge. While they seem easy to do, the xp doesn't coincide with a lv.13 synth @lv.11, i was getting 2000 physical xp (this being a leve quest). 1500xp being the baseline for an equal rank synth and +100xp for each rank over, I think this would be a rank 16 synth.
I made these @14 and was getting ~1900xp on the leve. That would make these 18 by your count. Post below from sukysuks would confirm if it takes a -100xp hit from each level higher. Either way...GREAT easy skillup synth with cheap mats!