That's about it Gavin. I've had many a crossing whistle performance cut short by an engine slipping out from under me. For those who know me, you will notice the whistling is rather short, concise and to the point, because I didn't want to keep my hand off the throttle any longer that I had to.
I remember the first time 463 ran as helper job way back when, John Bush and I were the crew. I let the road engine do most of the work part way up the hill until we sorted out how 463 handled and fired. About halfway up, I signaled the road engine to back off a bit, we opened up 463 and put her to work. Things were well in hand so I let John run his baby.
John was reveling in the justified glory of his handiwork blasting up the hill at Coxo when he reached for the whistle chord and let the D&RG freight hoot sing to the assembled crowd at the crossing. Just as he started, I felt 463 do a little dance that indicated a slip was eminent. I looked over at John, he was leaning out the window blowing the whistle, without the sanders on (I learned to always turn on the sand at a crossing). 463 made another shudder, then cut loose. With the whistle right in John's face, he didn't hear 463 break loose. I jumped off the seat, slammed the throttle closed, turned on the sand and opened her back up. No worries, no foul. I think John might have been a bit embarrassed though....