Just saying, you can just ignore responses, no need to act impolite, after all you asked questions and @lleachii took time to respond. This forum is not limited in any meanigful way, so his posts do not take space away for others to post....
Regarding to your topic, if you want to avoid fragmentation you should set your VPN interface vMTU such that vMTU+VPN-overhead <= link layer MTU... but that does not guarantee that fragmentation is not happening, as any other link along a network path might have a lower MTU. This is why protocols try path MTU discovery to segment/packetize their data accordingly. Often that works, but not allways... Typically TCP is affected most, and for TCP MSS clamping is a more side effect free way of achieving your goal....