Straight shaft yes. You may also want to consider bike handles and a hang harness. These are usually only used with a hard blade for better control but in your case I think it will help with the ole back. Take a little time to strap on the harness but it has a quick connect to the shaft so if you need to put it down to do something else it is easy to do. Just leave the harness on for when you come back to the trimmer. When the trimmer shaft connection is placed right it will just hand there perfectly balanced, then you use the bike handles to control it. The long straight shaft will get to the ground without you needing to bend over when it is all set up right.

Charles, I think you may be overanalyzing a bit here. I think you would be the person to get the advice from since you have experience with each type of Echo unit. I own a Homelite ST-275 straight shaft trimmer (flex cable drive) that is 15 years old. I feel like I take care of my stuff better than the average person, but I have only lubed the drive cable a couple times in the years that I have owned it. I have even run mine on several occasions with a brush blade (I know it is not recommended with the flex cable). My point is that I believe either will last her very well, without much lubrication hassle. Maybe I am talking a whole different level of usage than she would have, but I would estimate my trimmer has about 150 hours total usage on it. With that total estimate, I have lubed the cable on average about every 50 hours usage.

I have been manicuring my yard for almost 20 years with a simple Homelite Bandit curve shaft trimmer. I'm 6'1". The Homelite Bandit is at the end of it's road, it seems, still runs well for the age. I just finished fixing an new, but old, Homelite straight shaft trimmer that was stored in my garage for over a decade and although I have always been a fan of the curve shaft trimmer, I am leaning towards the straight shaft because of the reach, it seems to keep me cleaner, and also it seems as if it is easier to turn to do edging maintenance. I think today there are a lot of choices. Stihl makes the curve shaft FS 46 model which is a foot longer than regular curve shafts. It is a good option and provides the straight shaft reach and I'm currently considering for myself. One thing I should say on behalf of regular curve shaft trimmers is that in very tight spaces they are a lot easier to use than a longer shaft. So, each feature has an application. You will have to look at your stituation and decide what is the best fit.

I have experimented related to your concern. I needed to stand straighter vs bending and have a good reach (due to back issues) with a lighter trimmer. I found the following to be challenges but not real issues. It all came to me from servicing and owning 8-10 donated trimmers. Many donated working or after small repairs. I donate as working or parts to Yardmen that saved used parts. These Echo Power Heads can be challenging, time consuming (from lack of maintenance). All have worked well w/o any locked so far. Such as, an Echo HCA 2400 Power Head was on an Extended Hedge Trimmer that laid openly on the ground over a year. It runs well “directly on a string trimmer”. A killer PE-200 was given to me after starting easy and only idling. I finally got the carb repaired/adjusted as I promised the donator it needed (w/o spending a penny vs left over parts is “OR” Was My Killer). My 03 retirement is slowing on Donations And Volunteering, LOL! 1. My best powers were commercial grades engines with solid steel drive shafts and heavier power heads in some cases. 2. With a collection of trimmers (various brands) I started to mix & Match (WITH CAUTIONS) with Echo SRM mid grade engines (that had proven in 10 yrs of use to be a good power heads). 3. My goal was to use my Echo SRM 210 that has worked since 2000 w/o any problems. It was a straight shaft with a cable and string. It’s now a straight shaft and hard blade. The idea and hard blade head came from my Commercial Green Machine and “no more bending”. 4. I also wanted to keep a straight shaft with a string and did with an Echo HCA power head. 5. I also added a split straight shaft (for string/hard blade attachments) to an Echo PE-2000 Power Head.