AFIK, images showing enlisted Highlanders in feather bonnets with peaks date from circa 1815.
Looking at the question from another angle, however useful a peak might have been in Spain, the fact that these were detachable, tied on to the Highland bonnet with a tape, raises the question of how long they would have survived under campaign circumstances.
We are told that, by the end of the fighting in Spain, the 42nd marched in an unadorned, so-called 'hummle' bonnet, more resembling a battered shako with a band of dicing. The regiment's 'red feather' emblem, later celebrated as the 'Red Hackle,' was also reduced to a remnant.
"When the Regiment returned from the Peninsula in 1814, from being so long in the field, the
[ostrich] feathers had disappeared from the bonnet, and a little red feather on the front, same as on the shako [ i.e. the 'tuft'], had been adopted."
This was reported in William Melven's 'History of the Highland Regiments,' part of "A History of The Scottish Highlands, highland clans and highland regiments…" edited by John Keltie.
Although published in 1875, the section on the 42nd drew on the 'Memoranda' of Lt Col John Wheatley (retd) who had enlisted in 1817, aged 17, and was been active in promoting *Black Watch* regimental history (*n.b. Two words- with an even emphasis, as in 'Red Menace'!)
Another soldier recorded "We had lost all we had in the world, except the buttons on our clothes, that told our regiments" (Narrative of a Private Soldier in the 42nd Hldrs 1821)
By the way, Wheatley's description of post-war uniforms circa 1821 seems to be the source for erronious depictions of the Black Watch flank companies wearing bi-coloured hackles during the the Napoleonic wars, e.g. Wollen's 1889 canvas 'The Black Watch at Bay.'
'At this time there were a variety of heckles worn in the bonnet, another piece of bad taste — white for the grenadiers, green for the light company, the band white, and the drummers yellow, with each of them two inches of red at the top, and the other eight companies (called battalion companies) red.'
According to Wheatley, the regiment returned to all ranks wearing plain red hackles circa 1825
With regards to the Gordon Highlanders, the Regimental museum in Aberdeen depicts soldiers of the Waterloo period wearing bonnets with peaks. There is also a plain, shako-like peaked cap, surviving from the period, worn by a subaltern of the 92nd.
Clear as mud, eh?
