The Green and Whites had raced into a commanding 52-7 lead after 55 minutes, but then lost their intensity as the visitors mounted a fightback.
A combination of giving young players game time off the bench, two yellow cards and injuries saw Horsham lose their shape and concede six tries in the final 25 minutes.
All the momentum was with Bromley and the home side were relieved to hear the final whistle and hold out for a bonus point win.
Stocker, however, was pleased with many aspects of the display and labelled the closing stages as a rarity.
He said: “In the cold light of day, we got what we set out for – five points. The young team which at one stage had four 19 year olds playing and another four under the age of 21 on the pitch will learn from this and will only get better. Given their performance in the first 60, that is a very exciting prospect indeed.
To be honest, I prefer to dwell on the positives as the last 20 minutes was an aberration and something I’ve not seen before and unlikely to witness again.
For the first 60 we were simply excellent. Totally dominating in all phases and pulling Bromley’s defence all over the place such that we opened them up at will.
Most pleasing was the way we identified opportunities and then executed with a maturity that was well beyond the players’ years and a real insight into what this team can achieve. We played with pace and precision and despite being a smaller side physically, dominated at the breakdown which was a real pleasure to see.”
Johnny Whiting recycled the ball for an opening that put Arun Thompson over for a try, which was converted by Tom Johnson. On 12 minutes, a missed tackle out wide saw Bromley over the try line to level the scores at 7-7.
Horsham led again after a good advantage was played and George Palmer broke and off-loaded to Joe Wilde in support to score and then convert his own try. Johnny Ordidge then off-loaded to Giles Barber to cross and Johnson added the extras for a 21-7 scoreline.
The bonus point was achieved ten minutes before half-time as Johnson dived over following a recycled ball, while Joey Walker also crossed to make it 31-7 at half-time.
In the second half, a phased-based try was finished by Palmer and converted by Johnson, before Canice Gonzague scored from a kick return, again converted by Johnson.
Will Bell completed the Horsham scoring on 53 minutes as he crossed for a staggering 52-7 advantage. Bromley pulled a try back on 63 minutes by driving a maul over and three minutes later put another converted try down.
On 69 minutes another soft try with the extras made it 52-26, before three more tries, two of which were converted in the final ten minutes, brought Bromley to within five points as time ran out.
Report by Ollie Berry, WSCT