So you mean put them like the drawing?
Yes why not? Just use some foam or neoprene to fill the gaps and you should be good to go. Why you think you should need to change the layout? The only advantage I can see in the quadratic lay out would be that you have a bit more air inbetween which gives more oportunity to cool down the cells. But I think thatās not really a big issue.
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I prefer to have a tightly packed battery. Less chance of something breaking or coming loose. I have enough space to make it like in the photo, even with fish paper between the p groups.
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Hey man thatās alot of money to burn, please use fishpaper, hot glue alone is not enough I donāt want to see this build up in flames.
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Who said I am not going to use fish paper? Edit: I see how you could get confused. I just asked if I could skip using it but in the end I have enough space to use fish paper and even if I did not I would rearrange the pack in order to use it.
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Progress
I kept my batteries warm to make sure I got the best out of them. 
Let me know if you see anything dangerous and/or bad practice. @Acido @pjotr47 @psychotiller @deckoz
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First thing: welds looks very clean. Good job
Do you gonna put your battery under your board? Or in a case on your board? If so watch out with those nickel strips. I think they can hit the other packs if you place it in a flexible enclosure 
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They will be placed as they are in a Trampa monster box. It will be a whole ābrickā and all the p groups are held together with hot glue between them. There is a photo somewhere up in my thread that shows approximately how they will be placed in the box.
Beautiful spot welds! What welder do you have?
edit: The malectrics with a lipo battery
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Welds look really nice, make sure to test them every once and a while
Also I would put something like fish paper between the p packs
Or glue them together so they cant rub against each other
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Thanks. Technically it is two Lipo batteries. I tried with one at first but I could not get solid welds when testing nickel to nickel. Nickel to battery was fine but I am too anal to let these things pass. So I sacrificed another 6s 5000mAh battery to make 2 more 3s.
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You can get the same with the boss level, I will be running a 2p 5ah graphene 65c and will post some pics soon, should get even cleaner welds 
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Thanks. There is fish paper between the p groups and they are also welded together with hot glue. After it is finished it will be wrapped with Hudy battery tape and shrink wrapped.
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More progress.
I have another question concerning the BMS (Bestech D140 12S) I will use it as a charge only, so the load will not be connected to the P(-). Before I plug in the balance cables, I have to connect the B(-) correct?
Also it seems I must not connect the B(-) balance wire, is that correct? It seems strange they would include a pin that should not be used.
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Take a multimeter and measure the resistance between B- and the first pin. Itās 0ohm, means they both connected via pcb intern. Thatās why you donāt need to wire up the first balance pin from the jst plug.
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Looking good, wish my welds were this clean
For less work you could completely skip one of the parallel connections on each group, doing it only at the ends of the battery, they arenāt/shouldnāt be carrying any current anyway, and having them doubled does no improve current handling
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I wired my D140 bms like this 
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Finished!
And it fits 
You would not believe what gave me grief. The freaking heat shrink.
Nkon did not have the size i wanted in stock so I got a huge one that tried to make it work.
It did after 2 failed attempts and my OCD compels me to change it at the first opportunity.
Now that is see all that empty space I think I should have gone for a 12s8p or 9p.
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I know that and for the D140 there is continuity between the B(-) and the first pin. However I have read about a lot of BMSs going up in smoke if the balance leads are connected before the B(-). Connecting the B(-) separately ensures that even if I connect the balance connectors in the wrong order, I will not damage the BMS. I am not sure about that but since the manufacturer suggests that way of connecting, I figured it would be better to follow his instructions.
I didnāt said anything about the connection order. Just that the B- is connected via pcb with pin b- pin and that this is the reason why it doesnāt need to be wired. What you can also see in the schematics