A/C Cutout

After two long years I'm almost finished. I'm installing a 5,000 BTU A/C in the bulkhead and after turning it on and letting it run for two hours have found out that the hot air it produces is just being drawn back in to the unit's coils. The opening in the bottom of the trailer is 10X17 and the overall opening that the A/c is sitting in is 15X24. I could cut a hole in the front over the tongue and mount it there but don't want to cut another hole in the trailer. So basically, the A/C has poor air exchange. Should I cut the hole in the trailer floor larger or mount it in frt? I'd rather have it in the bulkhead since all the woodwork and work is done. Anyt suggestions?
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