It would be best if you started by understanding the fact that the scale is not the primary indicator of your weight loss and healthy lifestyle. The weight can vary significantly from day to day due to several factors such as bloating, water retention, etc. I would suggest using the scale once in a while (as you mentioned, every 8-12 weeks) and taking your body measures. I learned it from a doctor at cameronmch.com, and as he explained it to me, you have 2 variables to follow your progress. Last but not least, a seatback shouldn’t stop you from carrying a healthy lifestyle.