I have a question and I feel like my situation isn't super common because none of the folks I served with at other schools are handling the GI bill this way.
In undergrad (past few years), my state has a program that caps tuition and fees at public universities at a low amount for combat vets so it actually made more sense to use the old Montgomery GI bill instead of the post 9/11 GI bill for undergrad. I was told that since the MGIB was only 36 months and the post 9/11 was a full 48 months, at the end of the 36 months of MGIB I could switch to the post 9/11 GIB and continue on for an additional year.
My situation is I have about 6 months of MGIB left, can I switch to the post 9/11 when I start law school and have around 18 (6 months left from MGIB and 12 till the end of post 9/11) months left and then have the GI bill for my first two years or is the VA going to find a way to crush my dreams?
Post 9/11 GI Bill is also only 36 months of benefits. But, because you only get benefits during the 9 months of the academic year, it will be enough to get through a four-year program.
Now, specifically to your situation, if you contributed to MGIB, you are entitled to elect MGIB or Post 9/11. Once you elect Post 9/11, you may not go back. HOWEVER if you elect while you are still MGIB eligible, you may only transfer your MGIB months remaining. So if you only have a few months left, it isn't generally worth transferring.
Now, here is the interesting bit for you
38 CFR 21.4020 wrote:
(a) Limit on training under two or more programs. The aggregate period for which any person may receive assistance under two or more of the following laws may not exceed 48 months (or the part-time equivalent):
. . .
(4) 38 U.S.C. chapters 30 [MGIB], . . ., 33[Post 9/11], . . . .
SO, if you do NOT elect Post 9/11 until your MGIB is fully expended, you will be eligible for another 12 months of benefits.
You won't get as much for your first few months under MGIB, but 6 months Post 9/11<<<6 months MGIB+12 months Post 9/11
Edit to add: However, you should probably confirm with the VA. They are the ones who know the rules and make the eligibility determination.