I've heard some people theorize that the reason MP Grimlock and the seeker jets are smaller in scale than MP Optimus and Megatron is because of the economy. But one theory I haven't seen pop up is that Takara is simply making them the same scale to each other as they were in the original line. So even though Grimlock was bigger than Prime in the G1 cartoon, the actual G1 toy of Grimlock was shorter than the G1 toy of Prime. The seekers are also about the same size to MP Megatron as their G1 counterparts were. And the Binaltechs, which are unofficial MPs, are the right scale to MP Prime following this rule. So if this is the case, Soundwave should be the same size as Megatron and Optimus. If this is indeed the rule they're going by, I'm hoping they make an exception for MP Rodimus and Galvatron and have them simply be the same size as Megatron and Optimus. That should be the max size for a MP in my opinion.