使 colbacklow 透明

Question

我正在尝试创建一个带有 biskin 颜色的 tcolorbox，但我希望两面都是透明的，这是我的代码：

\newtcolorbox{mysolbox}{
standard jigsaw,
breakable,
sidebyside,
sidebyside align=top,
skin=bicolor,
boxsep=1mm,
left=8mm,
right=1mm,
top=1mm,
%colback=orange!30,
opacityback=0,
opacityframe=0,
colframe=black!5,
arc=15pt,
sharp corners,
%rounded corners=south,
overlay={
\node[rotate=90, anchor=north west, inner sep=2mm, text=white] (title@aux) at (frame.south west) {\bf\strut {\color{cyan} KCPE\examyear~}{\color{black}No.~\theqnumber}}; 
\path[ultra thick,fill=red!80!black] ([email protected] west)--([email protected] east) 
to[out=90, in=270] ([yshift=5mm][email protected])--
([email protected]|-frame.north) -| 
(frame.west) |- ([email protected])[sharp corners] -- cycle;  
\node[rotate=90, anchor=north west, inner sep=2mm, text=white] (title@aux) at (frame.south west) {\bf\strut {\color{white} KCPE 2019~}{\color{black}No.~1}}; 
},
%colbacklower=white,
%\kvtcb@opacitybacklower=0,
opacitybacklower=0,
}

opacitybacklower=0似乎不起作用。给我一个更好的解决方案。