you know how to make a 2 piece silicone mold? i wouldnt try to make a plaster mold of that for a couple reasons 1: its cruel unless already dead lol , 2: you will be digging and scraping hunks of lobster shell out of your plaster mold for hours to get it all clean ready for casting. i would make a silicone mold you could even just do a single pour and just cut the mold in half after its cured to make a simple two part mold and it will take better detail of your lobster, last longer/hold up better than plaster molds,and once it eventually starts to crack and wear out you can fill it with plaster and then make a new silicone mold from that plaster casting ! dont use rtv silicone though cause its a pain in the ass, use a silicone thats actually made for mold making they usually come in 2 part chemical batches that you mix part x with part y to make part z . if you wanna try rtv silicone ( the clear 100% silicone you buy from home depot) give it a shot but because it requires moisture to cure what happens when you try to creat a mold with it is it forms a skin and then the inside never fully cures and ruins everything, if you do choose to try rtv you have to mix some glicerine ( can be bought for a buck at cvs beuaty department)in with it first (how much depends on size of your mold, google it) this will not only prolong the skin from forming but will also give the moisture needed to properly cure the whole mold inside out.how do i know this crap? i used to be a makeup artist and have thousands of hours sculpting and hundreds of hours making molds of said sculptures. its a tedious thought out process that with one wrong move can destroy hours,weeks or months worth of hard work. need any advice on the process google monster makers and look at the silicone molding process. good luck