So, you're adding a 2,5m heatshield under the mk2 cockpit and then you're forced to add the rockomax brand decoupler that's like 5 meters tall. No more, install this mod ( you need to have module manager preinstalled ) and the little .cfg file will make sure all your heatshields have an extra function button named 'decouple'.

Activating this function decouples anything connected below the heatshield, so you can just connect the next stage directly to the heatshield, without a decoupler.

Please note that for the decoupling to work there MUST be a shroud on the heatshield, ie. you cannot connect the part to the heatshield without a shroud.

PS. in effect, this mod provides the function that 'jettison shroud' should provide out of the box.

Enjoy!