Abdulai Baggie’s first half winner gave Boro a priceless 1-0 Privett Park success against fellow strugglers Hartley Wintney.
That lifted Boro - who had failed to score in their previous five home league fixtures - seven points above the four-team relegation zone.
The victory was the seventh in 20 league games since director of football Mark Molesley was appointed at the end of November.
And it ensures that three clubs - Hartley, Harrow Borough and Yate Town - cannot catch Borough.
Bottom club North Leigh could still finish above Boro, but they would need to win their last three games, hope Gosport lost their last three, AND overturn a goal difference which is currently minus 15 worse.
Gosport, therefore, need just a point from games against high-flying Bracknell (away, April 15), Hendon (home, April 20) and Beaconsfield (home, April 22) to be mathematically safe.
And even if Boro did lose all three, North Leigh would need maximum points at home to Beaconsfield, away to Plymouth Parkway and at home to title chasing Truro City on the final day - plus some very large wins (or large Boro defeats).
Elsewhere in the Premier South on Easter Monday, two former Gosport strikers were on form.
Tony Lee struck four times as Poole Town stormed to a 6-1 victory at Dorset rivals Dorchester Town.
Warren Bentley, meanwhile, netted both Winchester City goals as they made mathematically secure of survival with a 2-1 success at Salisbury.