Assuming you have 5/5 STP merits, to 6-hit a 450 Delay GK you will have to either eat Carbonara (or some other STP food) or drop your haste from hands or feet. Since most of my playtime on SAM is end game content, I didn't want to eat Carbonara. Here are the two paths I saw (plus a fringe alternate case):
Path 1: TP in Rajas, Brutal and Hachi Feet- you will have 835 TP after 5 hits- will need 165 TP from ws. WS in Rajas Brutal and Hachi Feet
OR Rajas Brutal and Enkidu Subligar.
Upsides: Dusk Gloves for TP have +5 ATK which is better than the +3 AGI on Fuma Sune-Ate. Also +20 HP on Dusk vs +12 on Sune-Ate
Downsides: Requires extra STP in ws set in the form of Hachi Feet or Enkidu Subligar. Both are small downgrades to what you would be using if you didn't need to make up STP.
Path 2: TP in Rajas, Brutal and Hachi Hands- you will have 855 tp after 5 hits. You will still ws in Rajas and Brutal but you won't even need that STP to make your 6 hit.
Upsides: You will gain 2-4 ish STR, as well as some ATK etc. in your ws build by using more optimal pieces since you won't need any STP.
Downsides: Opposite of the Upside listed above- Using the lesser of the two TP piece options.
Path 3 (Fringe Alternate): TP in Rajas, Brutal, Hachi Feet and Attila's Earring- you will have 845 tp after 5 hits- will need 155 tp from WS which, similar to Path 2 above, can be achieved with no STP in WS set (tho you will still want to wear Rajas and Brutal regardless). DISCLAIMER: This choice is AWFUL is you opt for Bush. Earring from DM, however, if you have a diff. earring and this downgrade is a Merman's to Attila to improve WS set it's not that bad. It largely depends on what gear you have access too. I'm just trying to tell you how to get there. This is the least optimal choice of the three but may work for you depending on gear.
As far as which Hachi Piece is a better TP piece, the answer is neither really. You want them for the STP. Neither bonus effect will be active while you TP except when you hold TP over 1000 using the Hachi Hands. Hachi Hands also have 2 more STR than the feet so I guess they are a slight winner here though they are both a bummer when you consider losing 3 haste. But IMO a 6-hit is that much better than a 7-hit that it's almost always worth it though there are a few exceptions I suppose.
There aren't a ton of STP choices on the server so unless I am missing something, these are your two best options. I've spent a lot of time fucking with hit builds to the point where I actually wrote a spreadsheet to do all the calculations for me as I toggled pieces in and out trying to deal with Amano's retarded delay. Feel free to /tell me in game or PM me if you have any other questions specific to my response.
Edit: From what I am told, the STP on Myochin Haidate +1 (upgraded SAM AF legs) doesn't work. If that is ever fixed we could finagle some other builds here as well.
Edit 2: This is all based on the idea that you have NQ Dusk Gloves. If you have Dusk Gloves +1 then this is all a moot point. But if you have Dusk Gloves +1 then you should be asking about a 437 delay GK

Edit 3: Math changes ever so slightly if you have HQ Hachi pieces. If you have HQ feet you can TP in them and get same result as Path 3 without having the earring swap. HQ hands are overkill for 450 delay GK as the NQ hands will give you more than enough STP.