Once again, thank you @fiveten, @gblair, @chinesegeorge and @johnb. Few more details here
testfitting
I dryfitted the major parts, no surprises there (it is Tamiya after all)
I have removed the supports for the canvas as mentioned
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1. removed the tubes
2. removed the IP
and cut off the bits to hold the wheelguards. I have those in PE, so still have the opportunity to mount them.
The front have been opened up
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1. My fingers hurt after this sawing and cutting and sanding.
2. added some detail here too
not the best result, but it took an awful lot of time, so I shall probably have to live with that.
I drilled out 8 barrels and added some tube
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1. a little too large a gap
2. needs trimming
They will have some fittings and stuff, but I just wanted to dryfit them too.
Usually these improvised furltrucks had 8 barrels, but I am afraid that Tamiya made theirs too small, so I either have to source som bigger ones, add another two, or just make space between them? They will have chains installed anyway, so probably the last option will be used. comments encouraged!