Ha - Thats brought back a memory Theo.
After bad experiences with my first 2 cars (Fiat 127 and 128) I bought a reliable jap hatchback cos I was fed up of breaking down. It was quite a nice Mazda 323 2 Door in Black with racy side stripes and giant spot lights as well as all the other pimp stuff a 20 year old boy does to his pride and joy - All show and no go although the engine used to rev to what sounded like? (no tach) 8000rpm with no apparent ill effects.?
Anyway its side lights were separate units from the headlamps mounted above the indicators and junior had the brain wave one day of replacing the 5w bulbs with 21w bulbs making it look like Volvo/Saab daytime running lights. All was well with my new look until I noticed what can only be described as a pregnant bulge in each lens the size of the bulb head - The extra heat had softened and pushed out the plastic lens - Fearing a total meltdown I went back to 5ws immediately.!?