What do you think about that crafting?

[suzaku0zero0]

is it worth crafting Yasminkov 9000M ? at ext 4 it will have +114 r atk, but Im not sure if the dex detriment will make it hard to get high damage

[final_attack]

Well, it's depending on your build and how you play though.
If you got ZRC build (this meant you mostly go close range), then the dex won't really matter .... Or if you maxed Fury Crit, it will help a little too.

If you have access to Yash2k it would be better (well, it's the weakest *8, so it's kinda cheaper to re-grind (1.8k/try I guess) and re-affix (14k/try I guess)), so you can try the power of crafted weapon since it got the same potential as yash9k .......
and use un-crafted Yash9k as backup, just in case you find it better

As for your first question .... as far as I know, it "add" Hunter, so it's Ra-Gu-Hu that will able to equip them. Better ask others who craft using them. I cancelled crafting them earlier, since needed the money to make mizer

[Kondibon]

if I craft an assault rifle, and use クラス追加（ハンター), which classes will be able to use the rifle? hu and ra only? or hu and gu only? or all hu, ra, gu?

As for your first question .... as far as I know, it "add" Hunter, so it's Ra-Gu-Hu that will able to equip them.

What final_attack said. Rifles are always usable by both ranger and gunner, gunslashes are always allclass, and talis are always usable by froce and techer when extended. Weapons only lose multiclass status if it's not something considered "normal" for the weapon.