Just got the X-01 from Couurt 35 - obscene stats on this thing after upgrading it right to MK-IV.

Getting it was pretty easy (Level 31) - energy weapon and rocket launcher, no existing power suit or companion.

I just lured the Assultron (Legendary) down stairs to the side room and blasted him real fast. Used vodka and Psycho.

For the sentry bot thing, I had the triple rocket launcher. I faced him up top, shot 3 rockets and retreated down stairs into the side room, closing the door. After a minute or so, he retreats to his top right room. After that, I went up the ramp and launched 3 more rockets. I did that a couple times and he was dead.

Grabbed my X-01, cheers.

Side note: I think I needed expert/master hack/pick - I forget which, but the time you're here you should have those where they need to be.

You should avoid going too close to the National Guard Training Site and Army Checkpoint in South Boston, both Sites spawn complete X-01 Suits. The Blue Shipping Container is often good for a set leveled to what the character has, I have gotten T-45D, T-51B and X-01 Mark II from the location on different characters. The National Guard Armory is also good for a piece or two to assemble a third (or fourth) set of X-01 for a Companion to wear.

I avoid doing certain Quests that will send My character too close to the sites until after getting the suite of X-01 at the Court 35 Building after Level 28.

My current character is avoiding many Areas in the Game to see how many suits of X-01 can be spawned. I have a character that will have five complete suits when They get a Helmet from the Prydwen.

level 43 and piper and my girl are rocking identical T45 F suits. 27 steel and a circuit board to repair with 1180 ballistic and 970(ish) energy. I have 2 complete suits of X-01 but have no use for them. I remember in my first playthrough trying to use the X-01 and running out stuff to repair it.

My Minuteman Characters all wear T-45E or F, I discovered the Unique Chestplate from Cambridge Polymer Labs is either T-45 or T-51. I like it for Vatting Ghouls and the Minutemen Paint being restricted to T-45 only means most of My Characters get it early.