Reinforce countertop numeral for cutouts

I would try to screw and glue a steel sheet over the entire length, not too thin. (Stainless steel so that it does not rust over time)

Hi
Have you ever looked at the installation instructions for the individual cooktops?
They specify a minimum distance of 50mm at the front/back and 100mm on the left/right, but no 15 cm.
At least the distances in front and back don’t make sense, because if you subtract these 30cm from your countertop, your cooktop would only be 32 cm deep, and it would be similar for the sink.
Just take a look at the installation instructions there as well.

Best regards
Nordkäppchen

Hello,

In general, I would be cautious about simply screwing or even gluing a solid wood board on one side with a metal sheet. Wood expands or contracts across the grain depending on the humidity. If you screw a metal rail underneath, the rail should have elongated holes so that the screws (preferably flat head) can move according to the expansion/contraction of the worktop (even if minimal) - otherwise, the board may warp.

The principle of "elongated holes" is also nicely shown in the Numerär instructions. There, brackets with elongated holes are used for attachment to base cabinets.

Good luck, IKEA-Friend

Hi
Have you ever looked at the installation manuals of the individual cooktops?
They specify a minimum distance of 50mm front/back and 100mm left/right, but not 15 cm.

For the cooktop, yes - but for the countertop, 150 mm is required on the sides (see link to the manual).
Regards,
IKEA-Friend

So:

Gluing/screwing a solid wood panel to a metal sheet is not a good idea. Over time, due to the different materials, a problem will most likely occur.

How about, if it really has to be this panel, a "double floor." By that I mean screwing a second panel underneath the panel. This would then have to be selected by a carpenter and also adapted to the kitchen.

A very expensive matter, but if it serves the panel.

I am not an expert in DIY. But I am pretty good at improvising.... So here are my thoughts: A solid wood panel does not break that easily. You should just make sure that not too much pressure is applied from above at one spot without the panel being supported from below. In other words: I would rather focus on crafting some sort of support surface for the panel at the appropriate spot. So, screw additional wooden slats onto the base cabinets on which the panel rests.