I never had much luck with end-feds in the attic. I was a new ham at that time and did not fully understand how to ground the antenna effectively from up there.
However, I did install a tuned doublet in the attic and used it for over ten years with good results. Achieved WAS, WAC and 130 DXCC countries on CW. All of this was done on QRP.
I operated from a two-story townhouse condo in two different locations. Used a 33' radiator across the diagonal and added 16.5' on the ends to get 10-40M coverage. Later added slinkys to the ends to increase coverage to 10-80M. From overhead the basic antenna looked like the letter "Z".
Using borrowed rigs I could operate 160M feeding the complete antenna against ground. I found that quite amazing at the time.
The feedline was usually 300 ohm line. I snaked it from the attic to the basement shack using space along side a forced air duct.
Before trying the attic antenna I tuned a rain gutter & downspout assembly that covered 10-80M. I always recommend trying that first to get on the air quickly. My best results were usually on 40M and 80M followed by 20M.
Dave Gauding, NF0R