**I recommend fixing the suspension rail into the concrete, using a fixing arrangement designed to bridge the roughly 70 mm of plasterboard and insulation.** I would not use the cavity dowels you describe as the sole support for loaded kitchen cabinets.

This matches [Placo’s guidance for heavy loads on glued wall linings](https://www.placo.fr/fixation-et-accrochage): anchor through the lining into the masonry behind it. Your message doesn’t include the insulation datasheet link, so I can’t verify the particular 10+60 product.

The important issue is **support across the insulation thickness**. Tightening a long screw against the rail can compress the wool and damage the plasterboard. The screw also carries shear and bending across that gap, alongside the outward pull caused by the cabinet’s depth.

Two practical arrangements are:

- **A rated stand-off fixing system anchored into the concrete.** These systems are designed to carry loads through insulation. Fischer’s [TherMax range](https://www.fischer-international.com/en/products/fixation-on-etics-insulation/fixing-in-substrate/stand-off-installation-system-thermax-ii/stand-off-installation-system-thermax-ii/575227-thermax-ii-16-170-m12) illustrates the principle. Have the manufacturer confirm a model suitable for your lining, sustained cabinet loads, actual stand-off distance and METOD rail connection.
- **Local openings with rigid blocking secured to the concrete**, bringing a solid mounting surface out to the rail. The rail then attaches to that support. A competent installer can detail this, including restoring the lining and accounting for the cabinet’s lower contact points.

Compression sleeves around concrete fixings can form part of a suitable detail, but their presence alone doesn’t establish its load capacity: the anchor, sleeve and rail connection need to work together.

Your concern about adding cavity dowels is justified. **A “20 kg per fixing” rating cannot simply be multiplied by the number of screws.** It depends on the specified board thickness, spacing and loading direction; closely spaced fixings share the same vulnerable sheet, and the rail does not necessarily distribute the load equally.

The 70 mm gap also does not, by itself, establish that an enormous screw is needed. The required size and spacing follow from the fixing arrangement and its rated capacity.

Ask the installer or fixing manufacturer to specify the **exact anchor, concrete embedment, stand-off support and fixing spacing** for the full loaded cabinet run. That gives you a checkable installation detail. A recommendation to use unspecified cavity dowels is insufficient for this wall construction.