I've released a major update to Sandpit: https://www.moddb.com/mods/sandpit/downloads/sandpit-v401
Top of the changlelog is that it's on the latest Half-Life SDK now but under the hood the Model Menu now shows items from Opposing Force if you've got it mounted and the Pose Menu now gives you a lot more flexibility (the body changer now works for all bodygroups).

Sandpit is now also based on Basis (something like Spirit of Half-Life that I've been doing on the side).
New pose menuNew pose menu
You can follow progress at https://www.moddb.com/mods/sandpit and give it a vote for Mod DB's Mod of the Year if you're feeling generous too.