Nothings changed in the 30 years I've been flying, it's always been 45 fixed reserve for piston, I was also taught to add 15% veriable if I could carry it.
Having said this, I can understand why some warbirds may be having grief with this.
Maybe point A to point A operations, ie air displays and circuit trainers could warrent a lesser amount, no less than 30 minutes IMHO.