As most of my flying involves using the 2D panel, (to give total access to all the instruments without scrolling), I regularly add extra instruments to to my favourite 2D Panels, via the panel.cfg file, and suitable gauges....easy-peasy!
My Default Baron 58 has a number of extra gauges fitted to the 2D panel....

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I position them manually, using the X, Y, xx, xx coordinates...

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Doesn't always work with the VC panels.
Paul....G-BPLF...FS 2004...FS Nav.... 8-)...!
Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.