1.25 finger or less = low volume liner (9mm)

2 fingers = medium volume (12mm)

2 fingers or more = High volume (15mm)

I would get an accurate measurement of your MP size. With only one finger shell fit, you will need the 9mm volume, and you could go with either the 29/29.5 or the 30/30.5. It's a lot easier to stretch them out if they are too small than to try to make the liner smaller. If your foot is right at 30, I would go with the 30/30.5 as that is what intuition recommends. I had the same setup last season, and they were amazing. Prepare to have your mind blown. lol I went from "I can't wait to get these boots off" to "I don't really want to take these boots off."   These liners, paired with a good footbed and heat molding, make a great feel and fit. And lots of added stiffness.  I took the laces off and added a stretchy velcro strap to the top of the liner for the insano boots. 

Thanks for the info! I like the idea of the Velcro strap…..

Also, pay attention to the the sole thickness of the liner, as there isn’t a lot of volume in the Insano and a good insole is a must if you have much of an arch.

i'd 2nd what @lake-m-carver says. accurate mondo measurements of each foot right down to the mm is the starting point. take measurement after some activity that may simulate snowboarding activity since the feet will swell when active. ie. don't measure right out of bed. i measure 28.9 on left and 28.7 on right. mondo 29 boot shell and liner, two toe caps over larger foot when molding since my toe actually touches the very end of the liner. however, sticking a 29/29.5 liner into a 30 shell will only cause problems (scootch). get appropriate sized shell and liner. a wrap style liner will be stiffer than a tongue style. HD foam is not cushy feeling when you first put them on, but after properly molding and riding the performance is what you want. 

the stiffeners will add volume to your boot, but naturally offer additional heel hold since the insert "pushes" the foot back. no need to mold liners with these stiffeners, but it is recommended that insoles are used when molding if you use aftermarket insoles. oven molding is best since it will mold the whole liner to your foot etc. as well as to the shell of the boot that may help with any hotspots or pressure points that may occur from the shell. read up on molding if you're the diy type or bring it to a shop with an oven. i've paid 50 bucks for using a shop oven for reference, years ago; not the stack style that look like boot dryers... oven. 

note what @board-doctor says about boot volume as well. insano are known to be a lower volume shell. i'd keep the strings attached to the liner if possible btw. they're a nuisance when/if removing/inserting liner to/from shell for drying etc., but worth keeping. i find that Nidecker leans towards a lower volume snug fitted style shell as well. Burton or Deeluxe will have more volume for example. 

@tallcarver if you truly are a mondo 30, i have a set of SBC wrap (taller, higher volume cuff) and Power Wrap liners, used about 80+ days that you can have. these intuition liners can be remolded multiple times. some say 3, some say up to 5 or 6. just been sitting on them for two years since i sized down to a mondo 29 and use a lower volume lower (pro wrap or fx race liner). shipping from southern NH or meet up.