Hi, new here, but I wanted to weigh in since I had the same problem.
I love checking out different Linux distro's, but do so via Virtualbox. My first attempt at installing PCLinux Full Monty 64-bit I chose suggested defaults for .vdi size and allocation (dynamic), which is too small (8GB). After getting the first warning (needing 11GB), I ran the partition editor and found an odd, unrecognized logical partition at the beginning of the allocated space, leaving only 7GB for all the other logical partitions the installer wanted to create. I changed the size of the .vdi to 12GB, but kept the dynamic allocation. I still chose the "use the entire partition" in the installation menu, and this time it created the same odd size unrecognized partition but now it was 5+ GB in size. I tried backing up and choosing: "custom partitioning" (might be titled slightly different, but you get the idea), but still no go. It wouldn't get past the funky partition.
Finally I started over again, but this time I chose a 15 GB statically allocated partition (thinking perhaps the dynamic-ness might be interfering). In the installation menu, I chose: "custom partitioning" and gave 14GB to the root partition ("/") and a gig to swap. This time, everything worked out and I'm installed.
Of course, the scientific minded would be mad that I changed 2 things simultaneously, but Full Monty is a go, so who knows. Perhaps I'll try again with the dynamic allocation + custom partition and static allocation with "use entire partition" to sort out what the precise method of success was, but perhaps that's for the developers.
What I will say is that while Full Monty is big for a Linux distro (only 2 GB less than Windows 7 32 bit), it is gorgeous out of the box! Extremely complete (to a fault?), lots of classy effects, and unlike other currently available mainstream Linux desktop environments, it maintains function-driven interfaces, rather than being application driven. I'm quite impressed!
I'm not sure why PCLinux stayed off my radar for so long, but I'm glad I found it. I've been looking for an alternative to Ubuntu since Unity came along, never had much luck with Fedora (and its using Gnome 3 now anyway, which isn't any better than Unity IMO) and OpenSUSE is either plain KDE or Gnome 3 for main distributions, too.
So, for now, GO FULL MONTY!.