BI,

I would go with the weight tube route first. The weight tubes supposedly will not affect spine so if the arrows are spined correctly for your bow initially then adding the tubes should not do anything but add weight which is exactly what you are looking for.

However, if for some reason they do not work out then you are left with some 400 grain arrows which maybe not ideal for your desired setup but still may be totally functional if it comes down to the wire as it were.