William Britton hit four goals as the defending champions won 7-1 at Eslaforde Park to take a three-point lead at the top with a game in hand.
Alex Nicholls (2) and Jamie Epton were also on target for the visitors, while Thomas Buckberry got the consolation for Jamie Shaw’s side.
The defeat – their seventh in their last eight league outings – twinned with bottom side Ruston Sports’ withdrawal from the league, leaves Town Reserves second from bottom.
They complete their fixtures at home to Horncastle Town on Saturday (kick-off 3pm).
Sleaford Sports Amateurs, on the other hand, benefitted from Ruston dropping out of the league as they were handed a walkover win from Saturday’s cancelled match.
It means the Sleaford side need just two points to guarantee eighth place, and they could finish higher still, with four games in hand on Grimsby Borough, who lie above with just three points more having completed their schedule.
Amateurs were due to host Wyberton last night (Tuesday) and then entertain Immingham Town on Saturday (ko 3pm).