Fenlon has brought in eight players in a summer of transition, with Finnish striker Shefki Kuqi the latest.
Improvement has already been evident despite a 3-0 opening defeat to Dundee United in the SPL.
Hibs then fought back to draw with Hearts and won 2-1 at St Mirren last weekend to create optimism ahead of Saturday's visit of St Johnstone.
But Fenlon will not stop his rebuilding job before the transfer window closes.
The Irishman told Hibernian TV: "I think I'm still driving everybody mad about bringing players in; I think the board will be very happy when the window is done and dusted.
"But we're still trying to improve the squad. I still feel there are one or two areas where we need to strengthen.
"I think last week was a good example of that, where we didn't have a midfielder on the bench at St Mirren.
"Both Gary (Deegan) and Jorge (Claros) haven't played a lot of football and we had to leave them on where we could have taken one of them off.
"There are one or two areas we want to improve on. In fairness to the club, they are working hard with me to see if we can rectify that.
"We're looking at the midfield and one other area. It depends on where we are at the end of the window as to what we can do."
Fenlon added: "I have to be honest and say I'm more than happy with the squad we've got at the moment.
"I think the players we've brought in and the ones we've kept have worked really hard in pre-season and in the games. I'm delighted with them.
"Adding to the squad is about helping them and making sure we're strong on numbers so if we do have any injuries we can cope - but also being mindful of the fact we can introduce young players in as well.
"So we need to get that balance right and make sure we're covering all the areas.
"It maybe a case that if we can bring in one or two then some of the younger lads will be able to get some experience somewhere out on loan."
