More convoluted answer: one only per ship, but if you want a plasma fore and aft, consider the option of the omega fore and the Romulan aft. The Omega plasma torps travel fast, so travel out in front of your ship. The Romulan ones are much slower but seem to hit harder. I have this arrangement for my Romulan D'Deridex engineer and allows for turnabout to spew out the three Romulan torps before cloaking. If you like plasma in all its forms and looking to take advantage of sets, that is.
Comments
Name: Meaghan
Fleets: Tal'Diann, Imperial Romulan Fleet, Axanar Marines, LGBT of Starfleet, House of Ta'al
Characters: Dhivael i'Ratleihfi t'Kamemor (Rom-KDF), Empress Sela(Rom-Fed), V'alkris Morath(Fed), Kara Thrace(Fed), Jaeih Piccolo(Rom-Fed), Ellaria(KDF), Zylim Dukat(Fed)
More convoluted answer: one only per ship, but if you want a plasma fore and aft, consider the option of the omega fore and the Romulan aft. The Omega plasma torps travel fast, so travel out in front of your ship. The Romulan ones are much slower but seem to hit harder. I have this arrangement for my Romulan D'Deridex engineer and allows for turnabout to spew out the three Romulan torps before cloaking. If you like plasma in all its forms and looking to take advantage of sets, that is.
STO Wiki:
Omega set: http://sto.gamepedia.com/Omega_Adapted_Borg_Technology_Set
Romulan set: http://sto.gamepedia.com/Romulan_Singularity_Harness