I think you'd be dissapointed with just using a longer strop. (by which I assume you mean tack line?)
Based on my experience racing J boats, having an eased tack is great for deep running, but only when you have the crew weight to move about and heel the boat to windward. With no windward heel the kite will fall off to leward, blanketing itself behind the main even earlier than normal.
And when reaching an eased tack will just pull the boat sideways with no real forwards drive.
Unless this kite is free or a real steal, then I'd hold out for a larger one.
i think this is one of those occasions where consulting a good sailmaker is the best advice that can be given.
Give them the full details of your rig (mast height, J, fractional or masthead, kite halyard exit point, tack location, sheeting points etc) and let them get on with it!
Well, I specified mine to be cut higher than the previous one, as I have no bowsprit to clear it from the pulpit rails. (Yet)
Therefore my cruising chute is 'taut' when the tack line is tightened, leaving the tack of the sail an inch or so above the pulpit.
In cruising terms this means having a bit of a view under the sail!
As we only ease the tack line by max 12 inches when running deep (max 160 off the wind) its not disasterous.
With the tack taut, I can get the boat to sail up to 60 degrees, so quite usefully forward of the beam. Not perfect but OK for pinching up for a while.
The sail on mine is about 0.82 of the 'standard' symmetric spinnaker size, and starts to overpower the boat at about 16 knots.
I also had quite a generous cutaway to the clew, also to ease viewing issues, and catching on the guardwires/rails when tacking downwind.
On occasion, I goosewing the sail with a whisker pole, but most times it is more aggro than it is worth when we are shorthanded.
Mine is a full tri radial from Crusader, and sets as nicely as I would expect. 35ft boat with masthead rig. About 850 quid in 2005.
Thank you (and to you, flaming). The size (a stock size) I was looking at gives me about 14" spare assuming a taut luff between masthead and stem - and would be below the top of the pulpit. The next stock size down is not much larger than the one from my previous boat which is too small. Since there's £250 difference between the cost of a stock size and bespoke, its worth a bit of thought so all the replies here are v. helpful. Your '12"' easing is interesting. How much space at the masthead do you have?
I too have a tri-radial from Crusader which is great. I just told them what boat and they came up with the sizing. All I had to do was fill in the pretty colours on their diagram and pay them a reasonable cheque. They delivered on time and great quality although the tack strop as supplied was only just long enough.
Just got a selden bow-sprit fitted which I would recommend if you have an anchor on a bow-roller and / or a split pulpit