My Car: RHD, 855 2.5 20v GLE 1994

Hi there, after my previous posts regarding my AC inverter (posted as Rhoobarb2002) I have decided to wire direct to the battery due to cuurent issues, but..

I cant find a suitable cable entry point from the car interior to engine compartment, i was suggested that I look at the existing wiring grommets but the fit is too tight for 1 wire let alone 2, I did see an area 3 inches above the universal joint of the steering column, at the floor of the drivers interior space, it looks like an unused entry point. To describe it would be an eliptical area at a 30-40 degree angle with bolt/rivet holes eiter side. In the centre of this looks to be a circular 'cap' of about 1-1 1/2 inches in diameter, made of plastic or ceramic (to touch anyway) material. the 'ceramic' cap looks to be on both sides (both interior and engine compartment. Is this an entry I could use, punch out the 'cap' run the wire through, and pack the gap? It doesnt look like it would affect anything, especially if I secured the cables tightly. If not is there other possibilities for getting 2 x quater inch thick cables from interior to engine bay (passenger (left)or driver (right) side, I dont mind)

Many thnx in advance :)