You shouldn't need to be switching strap lengths for different exercises, tigress. Here's some info...since we can't post links.
Strap Length
Posted by Marjolein Brugman on Monday, September 1, 2014
Your AeroPilates reformer arrives with the straps already adjusted however occasionally they are not equal lengths and will require you to manually make the correction.
On our latest Plus reformers it is a simple change directly on the velcro handle. On past reformers there is a clip system under the platform and on the very easily reformers you need to retie the knot.
Your straps function to create a handle for your arms and legs as they work against the resistance of the cords.
The correct length can be established by lying on the platform with your arms straight up perpendicular to the floor at which point the straps should be equal and taut.
Should you wish to add range to your movement then shorten the straps by 2 inches.
Also, if/when the machine doesn't come back for an exercise, just increase the resistance up one cord (or whtever it takes). Marjolein only weighs 120 lbs. approx., so someone heavier would need to adjust resistance dependent on theirs. I think you'll find the machine more than sufficient once you get it set up correctly for you. 
A Dimitri Dazzler. Need I say More?