My friends have encouraged me to share my builds all in one place. So here I am. I was pretty surprised as I was getting everything ready just how many lots I've built in the past 8 months. So, gonna ...
I just wanted to thank you for your interest in my creations for Rflong7's 'Supernatural Island' ... that is most appreciated! :) ... you too have some fabulous looking builds in his thread and I am rather impressed!
I'm not sure if I can be of help and the following is what you've had in mind ... but you can use a LL rabbit hole easily on a 10x15 lot by placing it in the basement with room for either stairs or an elevator. You could probably reduce the lot size even further but I found it needs to be a bit larger than 10x10. My example has been built on a 10x15 lot with an 8x13 basement