Author here. Like I said in the post, the third constraint I had was something that would work with dd wrt - and that doesn't support l2tp. Thanks for the bit on the offline cracking though.
No worries, I understand your reasons for choosing PPTP, but I thought it important to highlight the consequences.
It is clear you have put a lot of effort into it though and it's more well written than a lot of guides I've seen, hence my interest in the first place!
