Good luck with it! Undoubtedly the most frustrating thing is not saving at typewriters. There are some chapters where you want to so badly! Trust me, if you do this challenge, you'll get halfway through a chapter like 3-1 or 4-1 and want to save so badly. Or pretty much before or after any really tough area. But because I'm crazy and want to make this hard and frustrating for myself, I resist the urge!
I'm finished with Chapter 5-1. Unfortunately I died once- my first death since 4-1. It was at the hands of the Iron Maiden in the laboratory area- which out of the ten Regenerators/Iron Maidens in the whole game is the only one that is compulsory to kill because it holds the key to Ashley's holding room.
Apart from that the chapter went smoothly enough- my tactic to use JJ's trigger happiness to my own advantage in the initial fight at the start of the chapter worked perfectly- I hid behind the rocks, let the soldier Ganados approach me, and when JJ let fly with a round from the chain gun, I hid behind the rocks. And watched as he gunned down a good number of the Ganados pursuing me! It was quite funny. JJ himself was tough to beat, but with a combination of a couple flash grenades, knife attacks while he was stunned and then shotgun blasts, I was able to nail him. Most of the other regular soldiers don't hold too many terrors- though I have to say the hammer soldiers (the large, fat, partially armoured ones) are a real pest and very dangerous.
My tactic with the Regenerators was fairly simple- one headshot with the Butterfly so as to temporarily disable their ability to bite- another Butterfly shot to the leg to knock them over (DON'T, I repeat don't, do it the other way around, or they'll bounce off the floor and bite Leon on the neck, and possibly bite through his jugular and cause him a gruesome death)- and then run, run and run. I will not even consider taking them on- on pro you would need at least 200 unupgraded Handgun bullets, or 50 shotgun shells, to kill them, or 5 Incendiary grenades- basically, in this sort of playthrough, where money is of no consequence, they are just not worth the ammo and effort expended. Indeed, if I tried to kill all of them I would have no ammo left at all.
Anyway, so to my battle with the Iron Maiden. The Iron Maidens, though typically described as upgrades of the Regenerators, are actually easier to take on than ordinary Regenerators on Professional, for one main reason:
-All Regenerators have a fifth parasite on their backs on Professional, not just the Iron Maiden variant- that removes the 'harder to kill element' that is present in Easy and Normal mode.
There's also another factor- unlike the ordinary Regenerators, the Iron Maidens don't have a bite attack (in any mode) because their mouths are so severely deformed. The bite attack is probably the most devastating and health consuming of all Regenerator/Iron Maiden attacks. Combining these two factors, I actually believe the Iron Maidens are easier than the ordinary Regenerators to deal with on Pro.
Nevertheless, the Iron Maidens aren't exactly nice creatures. Because of the amount of ammo they swallow, I decided to kill the one in the lab area by using just a couple bullets here and there to blow up the gas canisters, and mostly just knife the monster to death by using the broken window, getting a couple slashes in and then hopping back over the other side- don't you just love the way it can't impale you on its spikes through the open window? BUT I made the mistake of trying to slash him one too many times- never try to slash the Maiden more than twice after it has slithered onto your side of the window. I tried to slash it a third time, and got skewered to death- with 8/10 full bars of health- that's how health consuming their attacks can be on pro.
So when I repeated the fight, I made sure to limit myself to two slashes before I jumped over the other side- and eventually, after much slashing, the Maiden was history! The rest of the chapter after that was fine- just used common sense, and knife and kick, as much as possible!
Chapter 5-1 stats
Accuracy: 87%
Kills: 63
Died: 1 time
Now for 5-2, which will no doubt be a horrible chapter. Eeek.