La Veta Pass behind Steam

This looks like it's going to be a good summer for "rare mileage" fans: various operators are going to be running excursions over the Rio Grande's old La Veta Pass route and the Northern Pacific's Stampede Pass line. Stampede Pass has hosted excursions since BNSF rehabbed and reopened the line, but LVP is really rare mileage. It hasn't hosted scheduled passenger service since the D&RGW took off the San Luis from Denver in the late 1950s, and even that service was overnight. So daylight passenger trains crossing La Veta are rarer than rare.

The La Veta excursions are even going to be in steam, starting on Memorial Day. But here's the interesting thing - they picked up ex-SP Mogul 1744 for the service. She was a 1901 Mogul, a "Valley Mallet" designed for service on the flat expanses of central California. They were pretty speedy little things, but they were never great pullers - their maximum tractive effort topped out around 33,000 pounds, and they probably developed that at five or ten miles per hour, max. That's not much for a line as steep and curvy as La Veta. The Grande regularly used their L-96 class Mallets to pull the "Colorado and New Mexico Express" overnight from Denver - they developed about three times the TE of the 1744 - and those trains had fewer than twenty of the Grande's big heavyweight coaches, plus some mail and express cars.

So what I'm wondering is.....will the excursions be very short, very slow, or will they have a diesel engine coupled unobtrusively behind the engine like a big, vibrating baggage car?