So, the Maelstrom, is an interesting case. Its got one of the strongest active shield tanks of any battleship, but the lack of utility high slots tends to hold it back from solo use most of the time. It is most often used as a bait ship given its huge tank capability and decent number of mid slots.
There’s also the fact its a battleship, a class rarely used for solo PvP these days. Most people will simply assume you are baiting for a larger fleet and hit you with overwhelming firepower immediately.
Anyway, on to fits, you can essentially go down 2 paths, dual X-large Ancillary shield boosters or a deadspace XL shield booster (required since T2 shield boosters are pretty rubbish) and cap injection. The latter fits better, is more expensive and can sustain itself for longer. The former has better burst-tank capability and is cheaper. Almost all fits use 800mm repeating cannons or artillery (in a fleet or PvE setting) since the Mael has no inherent range bonuses.
Here is my suggestion for a deadspace injected fit.
[Maelstrom, injected]
Gyrostabilizer II
Gyrostabilizer II
Tracking Enhancer II
Tracking Enhancer II
Damage Control II
Pith B-Type X-Large Shield Booster
Heavy Capacitor Booster II, Navy Cap Booster 3200
Multispectrum Shield Hardener II
500MN Y-T8 Compact Microwarpdrive
Heavy Stasis Grappler II
Warp Scrambler II
800mm Repeating Cannon II, Republic Fleet Fusion L
800mm Repeating Cannon II, Republic Fleet Fusion L
800mm Repeating Cannon II, Republic Fleet Fusion L
800mm Repeating Cannon II, Republic Fleet Fusion L
800mm Repeating Cannon II, Republic Fleet Fusion L
800mm Repeating Cannon II, Republic Fleet Fusion L
800mm Repeating Cannon II, Republic Fleet Fusion L
800mm Repeating Cannon II, Republic Fleet Fusion L
Large Core Defense Operational Solidifier I
Large EM Shield Reinforcer II
Large Thermal Shield Reinforcer II
Hornet EC-300 x5
Valkyrie II x5
Warrior II x5
Standard Blue Pill Booster
Agency ‘Hardshell’ TB7 Dose III
Downgrade the guns to 650s if you wish, they will give you slightly better tracking at the expense of less range and damage than the 800s. This fit comfortably tanks over 1000 DPS without heat, while drugs are active, so should be able to last a while. The fit costs roughly the same as the hull which is about the sweet spot for T1 battleships.
And here is my take on a dual XL ASB fit:
[Maelstrom, XLASB]
Gyrostabilizer II
Gyrostabilizer II
Co-Processor II
Tracking Enhancer II
Damage Control II
X-Large Ancillary Shield Booster, Navy Cap Booster 400
X-Large Ancillary Shield Booster, Navy Cap Booster 400
Multispectrum Shield Hardener II
500MN Y-T8 Compact Microwarpdrive
Heavy Stasis Grappler II
Warp Scrambler II
Dual 650mm Repeating Cannon II, Republic Fleet Fusion L
Dual 650mm Repeating Cannon II, Republic Fleet Fusion L
Dual 650mm Repeating Cannon II, Republic Fleet Fusion L
Dual 650mm Repeating Cannon II, Republic Fleet Fusion L
Dual 650mm Repeating Cannon II, Republic Fleet Fusion L
Dual 650mm Repeating Cannon II, Republic Fleet Fusion L
Dual 650mm Repeating Cannon II, Republic Fleet Fusion L
Dual 650mm Repeating Cannon II, Republic Fleet Fusion L
Large Thermal Shield Reinforcer II
Large EM Shield Reinforcer II
Large Processor Overclocking Unit I
Hornet EC-300 x5
Valkyrie II x5
Warrior II x5
Standard Blue Pill Booster
Agency ‘Hardshell’ TB7 Dose III
650s are actually a slight advantage as they allow the ASBs to fit without having to go overboard on fitting mods. This loses about ~40 DPS and 10km range on the previous fit in exchange for being able to burst-tank close to 1900 DPS if it needs to (although sustainability is much poorer).
Regarding the gun choice, I strongly recommend the T2, not only do you benefit from the increased damage from the specialization skill, you get access to T2 ammo (recently buffed hail!), where barrage is pretty much a necessity when using autocannons on a ship with no range bonuses to hit things 20+km away for decent damage. You also lose ~100 DPS over the T2 variant.
Hope this gives you some ideas anyway
-Cat