This makes to tabs to be one in front of the other:
UserP = guiCreateWindow(0.10, 0.15, 0.8, 0.7, getPlayerName(player).. "'s user panel:", true)
Shop = guiCreateTabPanel(0.02, 0.13, 1, 0.8, true, UserP)
ShopTab = guiCreateTab("Shop", Shop)
Stats = guiCreateTabPanel(0.02, 0.13, 1, 0.8, true, UserP)
StatsTab = guiCreateTab("Stats", Stats)
I don't see the problem.
Thanks