[TenTec] Jupiert Tuning on 10M

[WmLB at prefer.net]

I have a behavior on 10M which strikes me as a little different. 

If I use my MFJ-989C to tune either my 80M dipole or my quad which is 
not quite resonate on the higher portions of 10M.. and I tune it for 
a 1:1 SWR, I find my maximum power out  is 75 to 80 watts. On the 
other hand, if I disregard SWR and tune the antenna for maximum power 
out (98 - 100 watts), I find that the SWR has increased to about 1.8:1

My inclination is just to tune for maximum power out and not worry 
much about the SWR unless it gets over 2:1 or so.

 I did change out my short runs of coax (rig to low pass filter, low 
pass filter to tuner, etc.) but it had no effect on this issue.

This behavior is limited only to 10M.

Is this unusual or not?

Bill
Costa Mesa, CA
Amateur Radio Station: W6WLB