Got my first F48T12 HO striplight on the weekend with included pair of Philips Alto F48T12/D/HO tubes.

I'm wondering if theres anything in particular to know about in terms of care for your HO fixtures VS regular F40RS ones. I have noticed that the ballast uses 1A even with no lamps, which makes me assume it wont appreciate EOL lamps left in place for a while.

Also interested in the differences in the F48T12/HO vs F40T12, Do they have the same gas fill etc? with just beefier cathodes? I like HO lamps with their RDC looking sockets, would consider under-driving those on F40 ballasts if compatible electrically

For F48HO there seem to be two types of ballasts generally available. The first is the type that runs lamps from 2ft to 8ft and will generally have a high OCV so 4ft HO lamps will generally instant start on them. All the examples I've seen use the HO style tall ballast can.

The second type usually has a narrower lamp range, from 2ft to 4ft and so have a lower OCV, 4ft HO lamps will generally rapid start on them. The one I have also comes in a smaller size ballast can, around slimline sized which opens the opportunity to retrofit regular F40 fixtures to HO.

I also find VHO lamps to work more or less fine on a HO ballast too, with the corresponding drop in power consumption and light output. Not sure about HO on standard F40 RS though, if I were to try I'd only use a rapid start ballast though since you want the constant cathode heating when underdriving fluorescent lamps to prevent the cathodes from getting too cold and sputtering.

At one point there also were SRS (semi resonant start) HO ballasts. They were 240v only and weren't that common. here's an example of one.