It seems I,ve come to this thread a little late.There,s some good advice given here.I drilled out all those pesky portholes too. Now,I didn,t worry about drill size.I just looked till I found one that fit the depression tightly and used that.
My fibre-optics fill the hull tightly leaving little room for a light source.I bundles all them together and painted the outside of them black . This way no light was lost.The funnel searchlights were tricky, But, I fudged on it and they work fair.I used a heat source to curve the ends so they would act like lenses to focus the light more.
The big problem is the wattage of the light. You have to keep it cool! For that I use six LEDS tightly together to replace the night-light bulb I was using.Not finished yet . will let you know the end result. TANKER-builder