adding inner forestay

well, in some books like Francis Kinney skene elements of yacht design and Brian oss Rigging book, the angle betwwen the lower shroud and mast less than 10 degrees is not recommended. and the lower shroud is recommended additional to runners.
well you say that if you lower the connection i can gain from the angle but the as heeling moment will be the same and as CE is lowered the sail force will be higher so the compression will be nearly the same...
What should i do? lower the terminal or not?

 

Dont put an lower aft stay opposing the inner forestay...you will regret the chafe it causes on the mainsail and batten pockets. Use running backstays.

 

but should i move the terminal down on the mast?

 

I'd leave it where it is, from the design, your vessel is already a few decades old & has survived this long, a year or so ago you gave it some extra versatility & balance as a cutter, unless there is a significant issue just sail & enjoy! Of coarse you could add a Baby stay, Check stays & Gooseneck struts if you really want to "lock it up" Jeff.

 

...less than 10 degrees is not recommended...
Yes, it is true. But in your case, the side-support effect is supplementary to the main support.
Main support is provided by the mast: side force is distributed roughly proportional to distances to nearest staying points -the closer the point, the bigger proportion of total lower stay transversal force it will take.
Runner, angled to the side, will help it, but normally will not carry a large proportion of load. It will act like some spring, slightly softer as the springs provided by the shrouds.

... What should i do? lower the terminal or not?
Generally, do what you like. Sail a few times in strong winds with small headsail on the lower stay only and watch behaviour of rig. If it do not bend/pump alarmingly between mast head and spreaders, setup should be Ok.
With lowered stay attachment, all the thing will be a bit stronger, but how much, no one will tell reliable just from the photo.

 

i can also anchor the runners a little bit forward when i am going upwind (there is a strong place that i can anchor) so it will take the transverse load better?

 

May be fit diamond/jumper struts & associated diamond stays, my Dad had this set up to a cutter rigged ketch, there was no runners required & worked well, how ever they can be "unkind" to an overlapping genoa but worked really well with a high cut non overlapping jib, this set & passes through the gap between inner & outer fore stays better any way. Jeff> Some further illustration/discussion...........

http://www.yachtworld.com/core/list...ner-33-2352125/United-Kingdom&boat_id=2352125

http://www.sailnet.com/forums/gear-maintenance/60995-i-need-some-rig-advice-please-3.html

 

That should be Ok.

 

and if i move the terminal down i will not remove the old pieces. i think it will be better for the sake of strength instead of unistalling them. At the moment, there is a T-terminal for the forestay and there is a bolt for the runner. under the bolt there is a piece to increase the wall thickness (like in the picture but there are four rivets and the hole is in the middele).
i am planning to leave the T-terminal base and the small plate in their places.

 

Once rigging is no longer attached, those backing plates do not help global strength of mast. They will be simply added weight aloft and one more possibility for galvanic corrosion.