Saw this on Alla this morning, now usually I wouldn't believe !@#$%^&*. However, the people that he refers to as players who can vouch for them are pretty well known on other message boards as being reliable people. I'm not a Leathercrafter, but I plan to test some !@#$%^&* out as a Clothcrafter using a similar method. Anyways, here it is.
From what ive read here and there, and noted on other servers.. No one knows how to make these!!! Seriously, i think Siren server is the only one with people who actively try to make panther +1s and succeed. I for one have made probaby 5x the number of panther +1s than my next closest competition.. so wanna know what i do? Good! Read and learn, dont !@#$%^&* because you cant hq them.
Fist off this only pertains to a 101+ leathercrafter. If you are less than 101 with armors, guild support should work, but also note that if you are 101 or above with armors, guild support does not matter.. i have made most of my panther +1s in Jeuno.. and only 5 that i can recall i actually used guild support.
When to synth:
I use a nice little chart to determine exactly when to synth. which i could spend all night doing ascii art to graphically depict it, but im not going to.. So, i'll just explain it the best i can.
Moon phases: There are only 4 moon phases that you need to concern yourself with.. These being Full moon (90%-100%-95%), New moon(10%-0%-5%), First quarter moon(40%-55% Up), and Last quarter moon(60%-45% Down). I put in the percentages just for clarification later.
Everyone knows that each moon phase is 15%, so there is 1 game day left off of each particular moon phase. SO: Since Panther Masks are a Tier 0 Ice synth, you want to synth on a game day with the absolute strongest possible elemental opposition to Ice. Which, in this case, would be a Firesday. But just synthing on any given firesday could return a hq, but the odds are greatly lower unless you actually find the best firesday to synth on.
The best firesday possible to synth on would be Firesday New Moon 0%. Why? Because when firesday falls on 0%, iceday will be at 7% and 12% game time.. NO iceday in that new moon phase, so there is no corresponding ice element in the phase to add any resistance to +1ing these. Sounds tricky huh? Not really. If you look here ~>
http://ffxi.lokyst.net/timer/crafttimer.html you see a nice crafting timer. Just set the maximum displayed days to like 1000 or something. When Iceday falls on 88% WXG, 38% WXC, 12% WNC, or 62% WNG, Synth on the following Firesday.
Now, I'm not going to explain this part.. just take it as i give it. When doing your panther synths, grab a bunch of them, you never know what could happen... FACE Northwest on Firesday and synth between 12:00 and 15:00 Game time, or synth at 21:00-24:00 game time in the moon phase lacking an iceday, and you will inevidably get a nice hq.
Sorry, im not great at explaining these things, but this also works for any tier0 synth, only times and directions are a little different..
The best ive done with Panther Mask +1s however was 7 out of 36 on new moon firesday 0% facing northwest at specified times. I may not make one every day, but i am well known for making Panther +1s all the time.. ask Alucards.. i made him one out of a total of 4 synths.. or Treefidy who loves to buy them from me and resell for profit at the ah

Good Luck...
Also, if you do something like 10 synths and dont hq one.. well, it happens. i cant make them hq for you, i can just tell you exactly when to synth them and hopefully all goes well. but they are still a lvl 100+ synth, so you cant hq them all the time. ^.^