As already noted, strategically applied "insulation" will help the warmth stay where you need it IN the cage. You can insulate the back & sides too, besides the top.
One more thing, & it's important: in your last photo, it appears your tank is resting on an electrical cord. This breaks down the cord over time, causing failure & an
unsafe home for your snake. I strongly suggest you buy some hi-density foam rubber weather-stripping from the nearest hardware store A.S.A.P.- it comes rolled
flat in different sizes, you want .5" thick & .5 wide (or close to that). It's easy to use, peel & stick (one side is sticky), cut to right lengths with scissors. Put your
tank up on "blocks" temporarily, & apply the weather-stripping to all the bottom edges of your tank, leaving 2 gaps (of about 1.5-2" each) on opposite sides, for
your cords to emerge AND for the UTH to "breathe" (for safety, so it's not over-heating & as instructed by UTH manufacturers). This weather-stripping WILL help
seal in the warmth under your tank, while protecting your cords...AND will make your tank very resistant to sliding (being accidentally pushed or sliding as when &
IF you ever have an earthquake...believe me, I'm from So. Cal. & this worked monumentally well for my glass tanks when I resided there & went thru large quakes).
This weather-stripping has a very small price-tag too, btw...it's a win-win-win.![]()