I am 6'1", 180", and I just squeak into the L/XL. Feels like I am going to scrape my face pulling the neck ring up or down over my head. I think that size core would be a huge mistake for you.
I have not tried the mix and match size trick, but have been thinking it. My Aqualung rep suggested it too. For you, I would be concerned Kevlar would not stretch enough. Do you really need that? Heavy, and takes forever to dry.
Yes, you can order with mismatched sizes, but I believe it will be Made To Order pricing and not standard price.
But... Here is your option - order a Sport, and then order the skin you really want. I haven't checked the Kevlar math, but right now at MSRP it costs $50 less to buy a Sport suit and a second Bullet skin than to buy just the Bullet suit. Sport plus Tech skin is only $50 more than just the Tech suit.
Haven't seen 2019 pricing yet, so do it now just in case. And if anyone in Chicago area wants to order a combo like that, PM me your email and I'll send a quote.